Network resource discovery: a European library perspective

Lorcan Dempsey
UKOLN: the Office for Library and Information Networking
University of Bath
4 August 1994

Paper presented to the British Library R&D Department
This paper is published in :
Libraries, networks and Europe: a European networking study. Neil Smith (ed).
London: British Library Research & Development Department, 1994
(LIR Series; 101)
ISBN: 0712332952
Please mention the printed version in any citation or reference
(c) The British Library Board
Introduction
The proliferation of new information resources, the rapid development of access and retrieval methods associated with them, and the unprecedented creation of global electronic information and communication resources have made the Internet an important component of many users' information environments.
A number of tools have emerged which facilitate the creation, discovery and use of network resources: they allow users to 'publish' on the network, to browse and search for resources of interest, and to organise or create custom views of resources. These are now the focus of intense research and technical development. Terminological fluidity is typical of any rapidly developing field. A number of terms are current, none of which has a precise referent: resource discovery, network information retrieval (NIR), network information discovery and retrieval (NIDR), network navigation, search and retrieve, access tools. For convenience in this paper I propose to use a new term, RADAR, whose sense is inclusive of these others, but avoids any partial or sectoral associations they may have. RADAR stands for Resource Access, Discovery and Retrieval. RADAR systems allow users to access resources; to discover what resources are available; and to retrieve found resources. It is also pleasingly apt for the purposes of this article as it places the emphasis on resource access and discovery, rather than on creation and "publication". This is not to suggest that these are not increasingly related processes. Gopher and WorldWideWeb, for example, are proving to be increasingly popular publishing mechanisms. In fact, advances in the ease with which resources can be published have not been matched by advances in a discovery apparatus, to the extent that immature resource discovery systems are now a major inhibitor of effective use of network information.

Publication tools
(resource space)	ftp	WAIS	Gopher	WWW	
Access protocols	ftp	WAIS	Gopher	HTTP	
Searching tools	Archie	WAIS
(Directory of sources)	Veronica	ALIWEB, wanderers and robots	
Table 1: Some common RADAR tools
Resources include files (documents, software, images), interactive database services (catalogues, directories, etc.), statistical and scientific data sets, and many evolving services. A resource may be a database, or a record within a database, a file archive, or a file stored in an archive, and so on. These resources are accessed in a variety of ways. RADAR tools are organised along client-server lines. Typically, users access to resources is mediated by a program which invokes one or more client programs as appropriate. Clients pass requests for services to servers which make resources available, and the interaction, the pattern of connection between clients and servers, and the resultant service to the user depends on the particular access protocols. For example, the gopher protocol allows users of a Gopher client to browse resources distributed across Gopher servers; the HTTP protocol is used for communication between WWW client applications (such as Mosaic) and servers.
However, no single access protocol allows users to reach all resources of interest: a number of distinct, if increasingly interconnected, resource spaces exist, defined by access protocols: Gopher, HTTP, ftp, WAIS and so on. Typically each resource space has associated discovery services - Archie for ftp sites, Gopher (browsing) and Veronica (searching) for Gopherspace, and so on. Each particular tool or system may support all, or only some, of the RADAR functions. Gopher and WWW, for example, allow users to access, discover (by browsing) and retrieve resources in an integrated way. In contrast, Archie is oriented towards discovery of files on ftp sites; it can be accessed in a variety of ways, and does not directly support retrieval of the 'discovered' resources.
Together these RADAR systems add richer support for information use to the earlier generation of services based on e-mail, remote login and file transfer. They will continue to develop in a number of ways. Several important trends can be identified, which will be examined in this article: 
	Integration of Internet resource discovery systems. These tools will continue to be enhanced and to diversify; it is not feasible or desirable to constrain the ways in which resources are made available in an environment of diverse providers, resources and users. However, after a first stage in which individual tools flourished independently, attention has now turned to questions of integration and interworking. There are three current strands of activity here:
1.	the construction of 'gateways' between RADAR systems and between RADAR systems and other resources;
2.	the development of agreed approaches to naming, addressing and describing resources to facilitate the propagation of information about resources;
3.	the development of agreed formats for document interchange
	Integration of Internet and other resource discovery systems. Although the Internet is increasingly rich in terms of the resources connected to it, it is still poor in terms of its ability to routinely satisfy users' information enquiries. Other information resources and services continue to be centrally important and provide access to much printed and other material which may be poorly represented on the network. Library resources are among these. A range of discovery systems to library materials also exists, many in electronic form. These include online catalogues and abstracting and indexing services, and various document order and supply services. However these are poorly integrated with each other and hardly at all with emerging network RADAR systems. The integration of resource discovery systems is a significant challenge, which is only beginning to be faced. One important aspect of this is that many RADAR systems are oriented towards the discovery and retrieval of files; they are less well equipped to provide application-level access to database resources, and do not support the exchange and further processing of structured data.
	Sustainable resource discovery services. Much of the RADAR emphasis has been technical, on systems. A resource discovery service  will integrate resource discovery systems in particular ways, will offer services within a particular domain and will add value specific to its purposes. To date, many resource discovery systems have been developed with voluntary or research effort and rely on the enthusiasms of individuals for continuity and support. This is now changing, and a number of organisations are investigating how to put in place sustainable, predictable and well-organised services. This in turn raises issues of funding and organisation.
This article examines these trends, and will:
	Give a brief general introduction to network resource discovery issues and developments.
	Suggest  some ways in which integrated resource discovery systems are likely to develop, focusing on the interface between library and Internet systems. A number of recent European developments in this area will be reported.
	Examine the emergence of sustainable resource discovery systems in the overall context of emerging Internet services.
It has been written with a library audience in mind, but it is hoped it can also serve to communicate some common concerns to a wider audience.
1. Internet Resource Discovery
There is a range of RADAR tools which was developed independently in response to particular applications, local constituencies or research interests. Gopher, for example, has its origins in the wish to create a distributed campus information service at the University of Minnesota. The World Wide Web was designed to assist in the development of integrated document and information services at CERN. These tools are more fully described elsewhere. Foster (1994) presents a directory, and fuller descriptions, taxonomies and pointers to further information can be found in Schwartz (1992), Obraczka (1993), December (1994), and Troelar (1994).
Some aspects of resource discovery 
One way of examining how the resource spaces identified above are organised is to look at the relationships between access method, metadata for resource discovery, and the resources themselves. Metadata is information about resources, and is of various types, and levels of fullness. In this article it is used inclusively to refer to names, locations and descriptive data which facilitate access or selection. In some cases, the metadata may be no more than a file name and location; in others, in library systems, for example, structured descriptive data may be manually created. Resources are the actual information objects of interest. This article will not say much about the resources themselves, but will focus on their discovery. Some access tools or methods provide access to metadata only (an online catalogue, for example); but it is also common that access to metadata and to resources are integrated, and that the path to the resource depends on the organisation of the metadata. The former tools are oriented towards discovery, the latter integrate discovery and 'publishing' functions. 
Archie provides search access to a central index of metadata. The resources are files 'published' on anonymous ftp archives. The metadata consists of a file name, and a path name on the host machine; it is already-existing data which is collected from ftp sites world-wide and organised for searching. Archie servers are replicated to provide redundancy and to improve performance; it also distributes the collection of metadata. Archie itself does not provide an access route to the resources themselves, other than returning the address. However many users, people or applications, of Archie will use it in conjunction with another tool, which can take the metadata returned from Archie, and resolve the addresses to retrieve the file.
With Gopher, the metadata consists of file, directory and other resource names, organised in a hierarchical directory structure to facilitate browsing seamlessly across servers. Resources include further menus, retrievable documents, searchable indexes, and telnet sessions. Browsing is complemented by searching tools, Veronica for example. Veronica collects existing metadata from Gopher servers. Search access is through the Gopher interface; the client queries a Veronica server and results are returned in the form of Gopher menus. Veronica servers are replicated. Current implementations of Veronica suffer from performance problems. Thus, Gopher provides browsing access to distributed resources, and search access to central repositories of metadata automatically extracted from these resources. Resources can be accessed on the basis of returned metadata, which includes a human-readable 'name' and access data hidden from the user, which the client interprets to achieve connection.
World Wide Web is accessed through a browsable interface organised by hypertext links. Links may not only allow documents to be retrieved, but may be created within documents. WWW is, then, more richly interconnected than Gopherspace. WWW has also been complemented by services which make searchable indexes of metadata. There are a number of 'robots' which extract existing data from resources and make it available for searching. ALIWEB takes a different approach; it collects and indexes manually created descriptions (Koster [1994]). Sites create resource descriptions for their services which are periodically collected into a central searchable database. A search will return a URL (to be described below), which enables a user's client to retrieve a selected resource.
Netfind, a white pages 'directory' service is different again, in that it offers a dynamic search for personal details about Internet users (Schwartz, 1993). Netfind maintains a 'seed database' which it updates by monitoring Usenet messages, Whois data, the DNS, and other resources. The 'seed database' offers hints about where to search further, based on a match with user-input name and other address details; Netfind uses finger and other protocols to dynamically search for further information, based on these hints. Netfind thus locates resources (in this case contact and other details about Internet users) based on the central collection of different kinds of metadata, which in turn support the dynamic process of investigating metadata distributed throughout different Internet services.
Some shortcomings of current Internet resource discovery systems
These tools have developed very rapidly, and, from a user point of view, several shortcomings are clear.
Browsing systems are not sustainable: it is not feasible to browse through highly populated resource spaces, even where hierarchical structure or other organising principles are deployed. Some structure is being introduced which divides up the resource space; for example it is common to organise resources by access method, by geographical or by subject area. In some countries there may be National Entry Points, a concept introduced within the European Gopher community, responsible for presenting organised, comprehensive access to national resources, typically using several 'trees', or lists, organised in these ways. Gopher and, increasingly, World Wide Web, are used for these services. These will be further discussed in Section 3. In this context, there has been much discussion of, and some experimentation, with 'subject trees', the organisation of resources into subject-based hierarchies depending on what they are presumed to be 'about'. Different approaches have been taken, but usually rely on some broad categorisation, maybe based on a library classification scheme. Again, this 'bookshop' approach is useful in a browsing context but will not scale up well as the volume of resources grows, and is subject to all the disadvantages of hierarchical and linear systems. In any case, 'subject', however defined, is one attribute only of potential interest to the user. Such organisation ignores other discriminating attributes - type in several dimensions for example (medium, function, cost, etc.). A second approach is to introduce a searching facility which indexes and makes available resource metadata for searching. As described above, this metadata may be extracted from the resource itself as with the Veronica service, or manually created, as with ALIWEB, or dynamically interrogated as in Netfind.
The second main disadvantage concerns the poor descriptions that are associated with resources. The metadata included in resource discovery systems is very sparse. One has often to use a resource, retrieve a file, or connect to a database to discover whether it is of use or not. In the case of search systems, the chances of retrieving relevant materials is lessened by the terse, and often non-descriptive, text from which indexes are created (e.g. file names in Archie, menu items in Veronica). One may waste a lot of time obtaining a resource which turns out to be irrelevant, or which is unusable because the appropriate technical equipment is not available. Future systems will depend on searching and browsing, but clearly searching becomes increasingly important in large information spaces. Also, as the Internet becomes a more mature information environment, with complex distributed products and services, the variety of attributes needed to characterize the range of resources also grows.. In this context there are a number of initiatives aiming at improving resource description, which will be looked at below. Related to this is the lack of data available to a user (or to the client application) before traversing a link or requesting a service. Some of the data above could be usefully returned before commitment - the size of an object for example, or its type. One could also mention here the complicated issue of quality. In a print environment one can make certain predictions about quality based on journal title or publisher. Quality cues have yet to be developed in the network environment, although one can imagine some scenarios.
A third disadvantage is the fragmentation that has already been referred to: it is not possible to access all resources through one system. Related to this is the fact that each system takes a different approach to the naming and addressing of a resource. It is not possible to uniquely identify an item: equivalent items may be differently identified, and non-equivalent items may have the same name.
One can note a major problem which will worsen as resources and users multiply. It is clear that replication and caching will be essential to improve performance and effective use of network links, and that more data is needed about traffic patterns and levels of use. This is true of resources themselves, but also true of metadata. Large global centralised indexes, for example, are not feasible, for several reasons. Although resource discovery systems will be important in this context and there is occasional further reference to this issue, it is also outside the scope of this article. (See Bowman et al 1993 for discussion of this issue in the context of wider treatment of scalability issues in resource discovery systems). 
Finally, although RADAR systems add a valuable layer of functionality, there are many resources to which they do not provide access, and the support they provide for access to heterogeneous document and database resources is limited. Many Internet information resources are one of two basic kinds: database resources which can be searched and file-based resources which can be retrieved. 
The main RADAR tools have typically facilitated the construction of, and access to, file-based systems. They support the retrieval of text and image files, binary files, and so on. What is emerging is a move away from content types which are specific to each system, towards one or more general registries of content types. One important such is the registry of MIME content types. What is likely to happen is that each access tool may contain a basic 'viewer' for common content types, whereas more specialised or complex formats will be passed to other applications. In this regard, the use of HTML within WWW is interesting. HTML is a simple SGML Document Type Definition geared towards presentation and display of documents, with hypertext links. There are several versions in development with varying levels of functionality. With the rapid take-up of WWW, partly because of the impact of Mosaic, there is growing debate about whether to enhance HTML to support the requirements of electronic publishing products, or whether it should be kept relatively simple.
Some RADAR systems, notably WAIS, have facilities which allow resources to be indexed and mounted on the network, allowing consistent access across WAIS resources. Within some other systems, WAIS indexing tools are used to generate searchable indexes. However, searching tends to be of relatively unstructured keyword indexes. At the same time the construction of gateways to heterogeneous database resources will become more common, and RADAR systems are incorporating facilities to ease this. For example Mosaic and other WWW applications incorporate a 'forms' feature, an interactive data input facility, to capture data which may then be processed for passing to another service. CGI, the Common Gateway Interface, is a specification for the construction of interfaces between WWW and other services, and is beginning to be widely employed. Sidebar 7 gives some examples of such gateways between WWW and some library servers. Gateways between Gopher and database resources have also been constructed. At this early stage, these gateways will implement their own mappings onto particular search systems, and convert data as appropriate. 
This is clearly a useful development, but raises longer term issues about information representation and structure. Much of the created structure, and hence usefulness, of the data in such resources may be lost or may not be understood by the user's application, and there may be no consistency across gateways. This is clearly an area in which much remains to be done. Discussing end-user access to growing numbers of heterogeneous databases in a slightly different context, Wiederhold (1992) notes that without some development work 'the information need to initiate actions will be hidden in ever larger volumes of detail, scrollable on ever larger screens, in ever smaller fonts. In essence, the gap between information and data will be  even wider that it is now' and that 'the poor user will be swamped by ill-defined data of unknown origin'. The emergence of specific protocols and structures which allow a higher level of interaction by capturing application-specific semantics will be important in this context. Z39.50 and X.500, for example, will provide access to certain classes of database, and facilitate the construction of gateways to them. The construction of gateways to Z39.50 resources will be discussed further below. There will also be a class of applications which provide some intermediate processing to consolidate structured data from various sources, and build services on this basis; Netfind provides an early example of such an approach: it provides a service based on its understanding of data from several other applications.
What will probably emerge are user applications which support a core set of common services (rather like Mosaic), but which pass control over to specialised applications for particular resources. The URI framework, discussed below, will be an important enabling technology in this context.
Integration and infrastructure
Problems are being addressed in a number of ways. Given the recent rapid rate of change, it is difficult to predict longer-term developments, but two main immediate strands are evident: firstly providing gateways between access tools, and, secondly, the development of 'infrastructural' components which facilitate the propagation of identifying, access and descriptive data about resources.
Gateways and integration of access tools
There are a number of approaches here:
	Combine multiple clients in one application. This inclusive approach has been taken up within the WWW community, and is one reason for its growing popularity. WWW clients typically 'speak' Gopher, NNTP, and ftp in addition to the native WWW protocol, HTTP. A user has access to several resource spaces through the same user application, Mosaic for example.
	Have a server which speaks more than one protocol. The 'gn' server for example, which can serve Gopher and WWW data. (This has been developed by John Franks. For more information see <URL:gopher://hopf.math.nwu.edu>)
	Construct gateways between tools. This consists in mapping the operations of one service onto another, and a large number of such gateways exist. Examples are WWW to WAIS, Gopher to X.500, WWW to X.500, WWW to Z39.50, Prospero to Archie, and so on. Of course, this will often result in limited functionality. Gateways are implemented between tools in order to extend the range of resources accessible through a single interface, or between tools with dissimilar, but, in the context of a particular application, complementary functionality. An example of the latter is the use of Prospero by Archie.
	Bowman et al (1993) describes another form of linking: data mapping. In this case, data may be collected from several sources using appropriate protocols and correlated using 'agreement' protocols. Netfind is an example of this approach. This approach may become more common as more services are built to exploit existing and emerging metadata. For example, Bunyip Information Systems are creating a service which will provide integrated access to Gopher and ftp resources based on combined indexes of harvested metadata.
These and other approaches are creating a richly interconnected information environment, which extends access and flexibility. It is probable that there will be further diversity of access tools, as new application areas with special requirements emerge, or as new approaches are taken to resource organisation. Interestingly, WAIS, Gopher, and now WWW, have been successively touted as the final solution. None has proved to be. However, it is likely that a constrained set of central protocols will emerge in common functional areas (e.g. browsing/organisation, indexing, directory services and so on) and that there will be less rapid turnover. This will benefit the trend to mature, consistent and sustainable services. For example one might see Gopher, or WWW, employed as 'front-ends' to the network, with directory, database and other services backended onto these in various ways. 
Resource identification: names and locators
Resources need to have a unique name, so that they can be referenced by client and server programs, as well as by humans. It is also necessary to be able to associate locations and access instructions with these names, to allow users (clients) to retrieve or use the named resources. In an Internet context, these requirements are being addressed within the context of ongoing attention to Uniform Resource Identifies (URIs). These are being developed by the URI Group of the IETF, who have achieved consensus about the gross details of what is required, though specifics are still being worked out. URIs will allow information to be shared about resources, facilitate the development of network publishing, support a variety of links (hypertextual, between a description and the object it describes, ...), and provide a core for electronic citations. (The motivation for this work is authoritatively overviewed in Lynch (1993), though it should be noted that this is a draft and employs an earlier vocabulary than is current practice).
An Identifier has at least three components: a Uniform Resource Name, zero or more Uniform Resource Locators, and Uniform Resource Citation or Characteristics. (This latter has not yet been fully worked out and is not discussed here. What is intended is some form of resource description along the lines discussed below, which contains  a range of metadata). A locator identifies a service (ftp, Z39.50, Gopher, WWW, etc.), and a parameter that needs to be passed to the service to retrieve a particular information object (Berners-Lee et al, 1994). A bibliographic analogue is a library shelf mark. Locators are not permanent (objects may move, or may be accessed differently) and an object may have several locators. There is clearly a need for another identifier which is not contingent on such accidental features as location or access method. A Uniform Resource Name is such an identifier; it is a persistent object identifier, assigned by a 'publisher' or some authorising agency (Weider and Deutsch, 1994b). A bibliographic analogue is the ISBN. They will allow resources to be referenced without regard to their location or access method. It is anticipated that 'publishers' will create URNs for the resources they produce or authorise other agencies to do so. There will have to be a registry process, for both publisher names, and URNs. 
URLs are beginning to be used in citations to electronic resources. They can be interpreted by WWW clients which will act on a user-supplied URL. They are also used to support the hypertext links in WWW. The developers of Gopher and other systems have committed to implementing them when they become stable. However, they are being used with a limited number of well-known access mechanisms (http, ftp,...), and have not really been exposed to a wide range of testing cases. They are still experimental, but there is strong backing from the tools-developers, and widespread agreement that a successful solution is now required. A data element has been reserved for them in the USMARC format. The URN is less stable, and has not yet been widely deployed. The protocol framework which will allow URNs to be resolved into URLs is also still being worked out.
Resource description formats
The creation of descriptions which are adequate to the range of possible user requirements is an intricate problem. This is for several reasons: features that need to be described may be complex or immature; it is not yet clear in what ways users will want to search for resources; new types of resource are appearing. This makes the task of devising standard descriptions difficult, and highlights the need for experiment. In fact, a data elements group set up under the auspices of one of the IETF working groups recently postponed work in this area, deciding that the variety of information objects to be described, and the lack of knowledge about actual user requirements, made standardisation in this area premature (Weider, 1994a).
Libraries, of course, have a long tradition of cataloguing and have developed elaborate rules and structures. It has seemed appropriate to investigate extending these practices to the networked environment. Strongly influenced by library practice, OCLC, the Library of Congress, the ALA MARBI committee and the CNI's TopNode project have all been looking at what data elements are required to describe resources. OCLC have experimented with the cataloguing of network files (not services) and results have been fed back into the USMARC standardisation process. Some of this work is documented in Caplan (1993). A proposal now exists for the use of USMARC to describe online resources.
A second area of activity was inititated by the IAFA (Internet Anonymous ftp Archive) Group of the IETF, who produced recommendations for the description of resources on anonymous ftp archives. A number of objects are identified ('user', 'organisation', 'siteinfo', 'document', 'image', and so on), and templates consisting of multiple attribute-value pairs defined for each. The authors recognise that these will need to be refined in the light of implementation experience (Weider, 1994b; Deutsch and Emtage). The IAFA templates are beginning to be developed in a number of contexts and are now probably the most widely used templates for fuller descriptions in the network environment. An experimental service based on the templates is now being run by Bunyip Information Services (Weider, 1994b). They are also used by ALIWEB (Koster, [1994]), and in the Dutch InfoServices Project (van der Werf, 1994a). (The IAFA Working Group no longer exists, but the IAFA templates are being proceeded within the Integration of Internet Information Resources Working Group of the IETF.)
The Text Encoding Initiative represents another important strand of activity. This is a major international project with input from those concerned with the creation, use and exchange of electronic texts in the humanities. It has produced a framework for the documentation and interchange of electronic texts based on SGML. The guidelines describe a TEI header, which includes such data as title, edition, size, publication, description of the source document, revisions and so on (TEI 1994). The header was designed with reference to library descriptive standards (for example International Standard Book Description and the Anglo-American Cataloguing Rules, 2nd edition). Such headers will be part of the files they describe; however provision is also made for 'independent headers' that can be exchanged separately. The relationship between such headers and MARC records is described in the Guidelines. The headers are not yet widely deployed, but their importance will grow with the implementation and take-up of the TEI Guidelines.
A fourth area is within the X.500 arena where some schemes for resource description have been developed (Barker et al, 1994).
Finally, an important future source of metadata will be the 'attribute' data described in Gopher+, and in the 'Head' of HTML documents. However, there does not yet seem to be any consistent set of elements for such data. Something may emerge in this area through the URC work mentioned above.
Other approaches exist, but these are the closest to main standards and systems streams, and seem to be most likely to be widely implemented. Within the UK, NISS has developed a format for use within their proposed service, which though influenced by some of the above work, has selected it own range of data elements. (See Sidebar 4)
Perhaps what is desirable is a 'repository' or 'dictionary 'of data elements, with various defined templates for specific requirements (for a citation, for a 'one-liner' in browsing or menu systems, for a full description for searching,...) and which can be represented in an encoding appropriate to the application area. It is clear that more experience is required.
Resource description - a note on creation and propagation
We can loosely characterise the current situation with resource descriptions as follows:
	Creation: Descriptive metadata can be extracted from existing titles, locations, or other resource characteristics (e.g. Archie, Veronica, various robots and Web wanderers). Metadata can be manually created by information providers (e.g. WAIS sources, TEI headers, IAFA templates). Metadata can be created by other parties (e.g. cataloguers).
	Content: Metadata is typically very sparse, unstructured and is often hidden (e.g. in README or INDEX files). There are moves to enhance the content in various ways; providing facilities for extra descriptive information (e.g. in Gopher+); growing attention to agreed, fuller formats as discussed above; more sophisticated post-processing of available data (see Sidebar 5), or more active searching out and consolidation of metadata (as in Essence, mentioned below).
	Propagation: It may be automatically collected by program (e.g. ALIWEB, Archie, Veronica, etc.). It may be manually collected. It may be manually 'forwarded' to some agency. It may sit alongside the resource, to be processed in different ways (e.g. Z39.50 'explain' service; Gopher menus; HTML Home pages). As briefly mentioned later, there have also been proposals to use the Domain Name System for propagation of identifying Metadata, or URIs.
	Organisation: It may be presented as a directed graph, as a searchable index, or distributed in some form of directory service. The latter is likely to become more important.
	Access: Typically search or browse.
One can see two complementary trends. One is the use of standard descriptions to support propagation of metadata. A second is the emergence of more programs which mine existing and improved sources for metadata and combine it in various ways. It is likely that each approach will be employed in more systems and services. However, there is some debate about their relative likely future effectiveness. At one end of the spectrum, the experimental system Essence epitomises an approach based on automatic searching for, and extraction of, metadata based on the existing content or characteristics of resources. It is based on the principle that 'different applications and different execution environments require customised means of extracting and summarising relevant information to support resource discovery' (Hardy and Schwartz, 1994). Essence provides a framework for recognising particular classes of file and carrying out appropriate processing to summarise their content based on their specific semantics. For example, author, title and other data could be extracted from Troff files based on the tagging inserted when using macro packages. The authors argue that such approaches are required in a global environment where it is difficult to achieve consensus, and which is characterised by the emergence of greater numbers of resources than can be effectively organised. At the other extreme are suggestions that Internet resources be individually catalogued based on human inspection, as is currently the case with the monograph literature. An intermediate position is that resource discovery systems will be based on the automatic propagation of descriptions created manually or otherwise, by resource producers; this is likely to be an especially important development. Again, future solutions will be various, as services adopt a mix of approaches.
A vision of integration
The development of global, sustainable resource discovery systems is seen as a necessary component of usable network information systems, but their actual design and construction are still matters for research and development. At this stage is might be useful to briefly look at one influential view of how the components so far identified might be integrated to provide workable services. Such a view is presented in Sidebar 3.
This vision is appealing, but it should be noted that much of the infrastructure upon which it relies is not yet in place. WHOIS++ and X.500 are not widely deployed to support the type of production services mentioned here, although working distributed directory services for this and other applications are recognised as urgent requirements. Their deployment in this way will require significant engineering and architectural work. At the same time, recent debate within the URI discussion list (URI@bunyip.com) has suggested that the DNS might provide an appropriate mechanism for the propagation of URN and URL data. An overall architecture for URNs has yet to be defined: URN structure, resolution protocols, and transponders all need clarification, as does their relationship with other naming schemes. This is not to deny their potential usefulness, which is considerable, but is likely that for some indeterminate period, systems will have to do without the desirable abstraction the URN provides (i.e. doing away with level 2). URLs will be quickly deployed, at least in association with common access methods. This is already the case with WWW. They provide some of the infrastructure which allows data to be shared, and wider deployment would confer immediate benefit.
Conclusion
In summary:
	Access tools: There will be more access tools and gateways between them; these may be a constrained set which between them provide mature and sustainable services.
	Metadata: Metadata will improve and be propagated in a variety of ways. Agreed ways of naming, addressing and describing resources are emerging.
	Resources: These are increasing in variety and volume. Although we have not considered them in detail here, we could suggest that developments will also benefit from a constrained set of data formats with translations and transformations as appropriate. Major issues of representation and structure have to be addressed in an environment of heterogeneous database and document resources.
Resource discovery systems will not be monolithic, but will be built from a number of interworking components. Services may be transparent to the end-user who may be unaware of the actual location of a particular resource, or of the systems which assist in its discovery and retrieval. 
If 'infrastructure' is defined by a constraint of solution choices at certain levels, which in turn provides a common platform, then infrastructure is most required at the metadata level, particularly within the narrower URI area. There will be less constraint at the access tools and data format level, though a limited set covering important requirements will confer benefit. However it is not appropriate to constrain certain components: the dialogue interface, for example. It is this shared platform which supports the construction of integrated services, based on gateways, dynamic sercies like netfind and on automatically extracted metadata. This 'platform' will also facilitate the construction of 'intelligent agents', which will benefit from structured metadata and a well-understood protocol framework.
2. Integrated resource discovery systems
This section explores some aspects of the integration of library and Internet resource discovery systems. Libraries now have several overlapping interests in network resource discovery systems:
	Many want to provide organised access to network resources as a natural extension to current services. Some have been quite active: training users, putting up gopher and web servers, and so on.
	They want to make library resources visible to network users. Many hundreds of OPACs are available on the Internet. However they are poorly integrated, typically only offering terminal access. The OPACs are available as reference resources; not as service points.
	A growing proportion of library materials will be in electronic format. They will have to be managed, described, and integrated in some way with paper resources. Some libraries are developing text archives, making technical reports and other literature available on document servers. It is likely that national and research libraries will begin digitising parts of their journal collections, especially out-of-copyright materials, for preservation and access purposes. It has also been suggested that libraries begin to perform archival and preservation functions for network information.
-	The greater emphasis on access to materials (as opposed to their collection) will require corresponding attention to systems support for delivery of integrated access-based services.
Most recent new systems and networking development in the libraries area has been concerned to expand and modernise the existing systems infrastructure, to develop and deploy standards and protocols for bibliographic and document delivery systems (Dempsey et al 1993, Dempsey 1992c). The Internet RADAR systems have generated much enthusiasm, but while libraries have used these systems to develop services and have introduced their users to them, the library contribution to improvement and further development of such systems has not been great. Until recently there has been little contact at a systems level between the two trends, although the integration of library and network resource discovery systems will be a major challenge in the next few years. Increasingly, for many classes of query, whether a document (for example) is available on a file server somewhere, in the users' local library, or in a document supply centre, will come to seem increasingly unimportant. The need to interact with separate resource discovery systems will be wasteful of time and effort, and will come to seem annoyingly arbitrary.
Library resource discovery systems
It might be useful to consider again the relationship between metadata,  access methods, and resources. The first thing to note is that most electronic information services provided by libraries are in fact collections of metadata. These include local and shared catalogues, abstracting and indexing services, and so on. This  reservoir is vast, but, as discussed below, is fragmented. It is made available through many heterogeneous systems. Access to these is typically by remote login; the move to client-server systems is only now beginning. Integration is typically by consolidation of data; facilities for distributed searching or navigation are not yet widely in place. 
The resources themselves, library collections, largely exist in paper form, although, as noted above, digital collections will grow. Delivery is usually by post, fax, or in various experimental services, through some form of electronic document delivery on the network (see for example, Moulton and Tuck, 1994). What this means is that, typically, the process of resource discovery and the process of obtaining the resource have not been integrated in any way. 
This is now changing, as users are being presented with services which allow them to request materials they find: from other libraries, from document suppliers, from other sources. However these are not provided in any consistent way: they are typically interfaced in proprietary ways with a particular search system. There is a standard for requesting materials, ILL (ISO 10160/1), and there are also proposals for providing such facilities through extended services of Z39.50, but these are not yet implemented in production systems. Furthermore, because of the costs involved and the nature of the materials being requested, this environment is quite unlike the current Internet environment in one important way. Whereas it might be possible to have unconstrained open access to some library resource discovery systems, OPACs in particular, it is not typically possible to have such access to abstracting or indexing services, or to library materials themselves.  Of course, some commercial services are emerging, based on deposit accounts, credit card charging or some other mechanism. At the same time, integrated desktop access to services is being introduced with particular closed groups of users, at individual levels, or within some organised framework of resource sharing and collective acquisition. In this way the library environment actually presents an interesting testbed environment for many of the services which will be required to support Internet commercial services.
In summary, the development of a unified service interface and effective integration of existing diverse services for identifying, locating and requesting items of interest is a major task which is only beginning to be addressed. Typically, these services are poorly integrated with each other and hardly at all with emerging network resource discovery systems. The bibliographic resource is fragmented. Solutions will depend on agreements between the entrenched systems of service provision, at different stages of development, a slowly evolving protocol framework, and, often, on a framework for commercial transactions which is still immature. Requirements and trends are discussed elsewhere (Dempsey, 1992b; Dempsey et al, 1993; Dempsey 1993b). The focus here is on those components of emerging library services that will be important in the context of the type of integration we are discussing: access protocols and the sharing of metadata. I consider each of these in turn, and then briefly conclude this section with some prospective service scenarios.
Access protocols
The emergence of Z39.50
Most of the RADAR tools are organised along client-server lines. However, most library applications still belong to an earlier phase, characterised by terminal access to multiple self-standing applications. These tend to be monolithic and enclosed, with diverse search and user interfaces. There are few real distributed library applications. This is beginning to change. Search and Retrieve (ISO 10162/3) and Z39.50 are emerging as protocols of choice for the construction of distributed retrieval bibliographic information services. (Z39.50 is a NISO standard which is a superset of SR; there have recently been proposals to merge the two). Z39.50 has facilities for managing queries and returning results. Importantly, it also incorporates techniques for switching between query languages, allowing the user interface to be separated from the search engine. In this way a single user/dialogue/search interface can access multiple diverse servers, and similarly, a single server can be accessed by multiple user interfaces. Apart from the general advantages conferred by the client-server approach, Z39.50 is strategically important for several reasons (Dempsey, 1994):
The first is that users cannot use endlessly proliferating different user interfaces. Z39.50 does not prescribe a standard user or dialogue interface; it offers a standard way for a particular user interface to communicate with servers. The user interface may be implemented in association with a standalone client, or may be part of an existing product such as an OPAC. This is now the type of application that is doing most to drive SR/Z39.50 development.
Secondly, it will support some of the program to program communication that will be necessary to develop bibliographic information systems. Examples of such links are between a union catalogue and circulation systems to determine availability, or between a search system and holdings files, to determine location. This type of application is not now common.
Thirdly, because it supports retrieval, it will be an important transport mechanism, for bibliographic data, but for other objects also. This is important, not only for the delivery of structured data, as in cataloguing environments or where data is imported into personal bibliographic systems, but also where further processing or manipulation is required. For example, one could imagine an application formulating a query to a serial holdings file based on its understanding of the content of a structured record returned in the search of a table-of-contents service.
Finally, because it will make bibliographic resources available through publicly known server interfaces, it will facilitate the integration of library resources into a range of RADAR applications. For example, in the scenario proposed in Sidebar 3, one could anticipate that some access and delivery services would be based on Z39.50. 
Z39.50, then, enables bibliographic resources to be developed as real network applications supporting a variety of distributed services. It should be noted however that it does not support any organisation of the resource space defined by Z39.50 servers. It is a point to point protocol, which does not support navigation, or forwarding of requests between servers, or consolidation of results from multiple servers. This functionality has to be built into applications which use the protocol. For example the Irish IRIS service (see Sidebar 9) allows a user to search across the six diverse OPACs of participating libraries in a single operation. The user application opens up separate connections to the individual servers.
As discussed above, RADAR tools typically give low level access to heterogeneous data resources. Because Z39.50 was developed and is largely implemented within a limited and relatively well-understood applications area, it can operate at a higher level of abstraction. Various intermediate formats are defined, in which the syntax and semantics of searches can be expressed, and for the transfer of more or less structured data. In this way clients and servers share a common understanding of the data to be retrieved, and the operations which can be carried out on them. These need not be the subject of separate agreement. It thus avoids the complexity of multiple mappings in an environment of diverse client and server applications, and makes it possible to provide bibliographic resources on the network through high-level server interfaces. Client applications do not have to know how data is structured on server databases; queries can be addressed not in terms of data objects (tables, fields, etc.) but in terms of information objects (author, title, etc.) (See Lynch, 1990). This will facilitate the development of distributed services, but also the construction of gateways from other systems.
Access protocols and integration
Currently there is very low level integration between bibliographic systems and RADAR systems. Users of Gopher or WWW, for example, have to drop into telnet sessions to access library or other bibliographic systems. As noted above, library systems tend to be closed, a range of individually accessible islands. A number of developments are possible.
	One approach would be to make bibliographic data directly available through RADAR systems. This is not now common, and is unlikely to be adopted widely for some classes of data because of the probable unnecessary duplication involved, as the bibliographic record shares a number of functions. For example, a typical OPAC provides access to holdings and circulation data as well as to descriptive data about books. However, it is probable that a number of commercial or research services will appear in this way, anxious to be easily integrated into their users' normal information use behaviour (See, for example, DowVision (McCall, 1994).)
	Several library systems will bundle RADAR system clients with their applications.
	There are now also several RADAR system to library system gateways. Some examples are given in Sidebar 7. This application level link is a big improvement. It allows users to remain within Gopher, or WWW, or whatever system they are using, and will also typically enable the return of data which can be further used.
	This is clearly useful where a particular group of users wants access to a particular resource, and it is likely to become more common, particularly in the WWW environment where gateways of various sorts are becoming more common. However, although you overcome some of the tedium of having to separately connect to a different system, it has limitations in an environment where a user wishes to use several such services. It does not address the question of heterogeneous search and dialogue interfaces, and functionality is inevitably lost. RADAR systems are typically stateless: they do not retain data from one connection to the next. Accordingly, one issue facing the builders of such gateways is how to mimic the concept of a 'session'.
	A more sustainable approach might be to implement RADAR systems to Z39.50 gateways. WWW to Z39.50 developments are discussed in Sidebar 8. In this way, a user can access a range of services through the same WWW search interface.
	Finally, again as suggested in Sidebar 8, one probable development will be a level of integration based on the propagation of URLs, in which an application can invoke a Z39.50 client having interpreted a URL. URLs for Z39.50 services are currently being developed.
Metadata
Bibliographic metadata
There are two levels of metadata: metadata about library resources (i.e. bibliographic records) and metadata about catalogues and other bibliographic databases as resources in themselves. 
Libraries have invested heavily in the creation of the former in the shape of their catalogue records. These services allow the user to 'discover' monograph resources, and in some cases to request their delivery. They often contain locators in the form of library holdings data. In union databases, one could construct a locator from some concatenation of shelf mark, holding library, etc. Typically these locators are interpreted by humans, but in some cases they are interpreted by program and enable requests to be routed to the appropriate libraries. A complex apparatus exists for the creation and sharing of records (Dempsey, 1990), and in many European countries there is a consolidated resource, in which the national monograph holdings, or some significant portion of them, are represented (Dempsey, 1992a). In the form of OCLC, there is also a significant international resource which contains approaching thirty million individual titles reflecting very many more holdings. Other large reservoirs also exist. These services are funded in a variety of ways. Some receive direct government support; some are cooperative ventures which recognise the value of shared effort and a consolidated resource; some are more commercially oriented. Each serves a more or less closed community of users; only some are 'publicly' accessible.
Libraries also provide access to abstracting and indexing services in a variety of ways. These are largely created outwith the library community. Recent years have seen a move to greater provision of end-user services, either on CD-ROM or by funding the acquisition of data for use within defined communities of users. Typically, this is at institutional, consortial, or, in a few cases, at national level. An example of the last are the databases made available within the context of the datasets policy in the UK, an initiative aimed at creating the conditions for mass use of bibliographic and other data in the UK academic sector (Law, 1994). There is a growing trend towards unmediated end-user services, sometimes in conjunction with document ordering facilities. However, usually these resources are subject-oriented: they are not representative of any particular library or other collection. They do not have associated holdings or location data. Some newer 'table of contents' services now exist, which do have links back to particular journal resources. One potential problem in the UK, and in other European countries, is that journal holdings information across libraries is often incomplete, and where it exists, is not maintained in a standard form.
As noted above, the bibliographic record resource is fragmented, and resides in many databases of varying scope.  Many of these, library OPACs primarily, are freely available on the Internet, but others, union catalogues, national library resources, and abstracting and indexing services, are often available to certain closed user communities only. Typically, it is not possible to search more than one of these at a time.
At the second level, that of describing the catalogue itself, or the collection(s) it represents, as a resource, there has been limited library effort. Schemes such as Conspectus, developed by the Research Libraries Group, exist, but are not widely deployed. However it seems obvious that a corollary of making catalogues and other resources more widely available is the creation of metadata which would allow a user, or user agent, to select them as resources of potential interest. There is little consistent guidance in terms of special collections, subject strengths, ILL or external reader policies, and so on. Investigation of what ought to be described, and how to make it available, would be a useful project. This data could be propagated through resource discovery systems to aid in the selection of appropriate resources, as well as having other uses.
Integration of metadata
One can imagine a number of different scenarios, with at least two main strands of development.
	Centralised consolidation of resources. This is happening in the InfoServices project described in Sidebar 6, where descriptions of resources supplied as IAFA templates are being converted to the Pica MARC-related format for online resources, and are being added to the Pica database.
	Integration by user application. Some examples will be given below.
These will be facilitated by a constrained set of formats for describing online resources: MARC, IAFA templates, TEI headers, and so on.

Conclusion
Several integration routes have been identified above, which are likely to be implemented in various combinations in actual applications and services:
	consolidation of descriptive metadata; 
	gateways between access tools;
	integration of 'library' access methods and metadata services in the integrated information services described in Sidebar 3, based on publicly defined protocols and formats, and the propagation of URLs.
One can imagine how applications will exploit emerging infrastructure to build consolidated services which cross current resource discovery domains. Some examples are:
	An application which accepts a user search and runs it against Archie and a bibliographic database, consolidating the results for presentation. The user selects required items. The application interprets the URLs and takes appropriate actions, starting up an ftp client or document ordering system as appropriate.
	One could extend the service described in the InfoServices project in various ways. For example, when a user retrieves one of the records for an online document, the 'Pica system' could interpret the URL, and start up the appropriate client to retrieve the item
	One could imagine a Mosaic type application which included a Z39.50 client, or which could start one up where required (see Sidebar 8.)
These are simple scenarios. Many others could be imagined. It is on the basis of this type of infrastructure that the 'virtual library', and personal information 'agents' which search and consolidate data on behalf of their users, will be built. I have emphasised Z39.50 and metadata, because they provide scope for early experiment. The overall solution will be more complex, but some experience is now required.

3. Sustainable services
Introduction
Developments can best be understood against the wider background of evolving Internet services. Elsewhere I have suggested that we can identify four phases in the growth of Internet infrastructure which have emerged successively but whose characteristic users and service orientations continue to exist side by side (Dempsey, 1993c). These are: 
	Esoteric. The networks emerge as esoteric instruments of the physics and wider scientific community. Resources are largely computational.
	Community. Their use expands rapidly, and they become central to the communications, research and collaborative habits of many in the academic and research world and increasingly beyond it. For a growing group of initiate users, the network has become a type of communal mental space, which is integral to communications and work behaviour in ways which are often quite difficult for non-network users to understand. The popularity of e-mail was not foreseen, but it was soon widely used and the network has become a communications environment. Information services also began to be more widely used: ftp archives, remotely accessible databases and so on.  The large number of electronic discussion lists and bulletin boards, and the emergence of the RADAR systems are evidence of flourishing communities of network users.
	Academic and research information infrastructure. The networks are recognised as integral to the academic information environment and as strategic resources for research and learning. This stage is marked by national funding for information services, institutional interest in opening up views of Internet resources to their users, and the growing presence on the network of commercial and non-commercial information resources of interest to the academy. It was realised that the Internet was sufficiently well-established to become centrally important to the way information is created, distributed and used in the academic community. Libraries and library organisations, professional associations and learned societies, and academic publishers are all considering how to respond to an environment in which the network is centrally important to their constituencies. Commercial organisations are connecting subject to acceptable use policies, and various government agencies are considering how to make services available. It is in this stage that the RADAR systems come into their own, enabling a change in which the network is no longer seen as a collection of systems, but a collection of information services. Innovative indigenous information technologies and services emerge.
	Public Information infrastructure. Commercialisation and privatisation continue apace, and the Internet becomes part of public infrastructure. Depending on national context, a 'private' Internet sector may continue to be funded for the academic community, with certain restraints on use. However, this is one component only of a bigger Internet to which it is linked. The Internet will be a diverse information and communications environment. An important requirement before much of this can happen is that a protocol framework for billing and charging be developed.
This provides a useful, if somewhat reductive, framework, in which we see the Internet successively acquire computational, communication, information and business layers. Clearly, there are different national contexts, but one could suggest that European countries are in the third stage with regard to network infrastructure. The 'academic' networks are becoming pervasive, upgrading their links, and moving to a more professional and service-oriented attitude in relation to the communities they serve. Of course this is not to deny the importance of growing public Internet services, such as Pipex in the UK, national EUnet providers, or several Nordic providers, but, only to suggest that, while things may change quickly, stage three is still the dominant Internet culture in Europe.
In the US, there is a complex patchwork of Internet provision, supported by a variety of funding streams, to the extent that a public infrastructure now exists. There is also an active political, policy and business debate about the development of the so-called National Information Infrastructure. A different public culture, which implies different  relative levels of private and public funding, has moved developments in the US much more quickly towards stage four.
One can note a parallel development with information services. Corresponding to the three latter phases, one can see three strands along which more or less sustainable initiatives are being developed. 
	Community. Information services began to be made available with begged, borrowed or stolen machine and human resources. Much is nugatory, of little interest, or poorly supported; some will flourish and move to a more sustainable basis where a need has been identified. Some 'community' initiatives are network journals, bulletin boards and discussion lists.
	Academic and research infrastructure. Libraries, government information, data archives, academic information services, network information centres, other initiatives supported from research funds or other sources.
	Commercial services. A range of commercial services is appearing. Many of these are exploratory and provisional, as players work towards an understanding of how commerce can be carried out on the network. Funding and charging models need to be tested; an enabling protocol framework for charging, security and EDI is required; and cultural and behavioural norms need to be established (how, for example, do you advertise on the Internet?).
This pattern repeats itself with access methods. Development work is progressing in the three overlapping streams characteristic of stages two, three and four:
	Community. Much of RADAR development has a technical focus, and has flourished in the Internet culture which owes much to cooperative work, the enthusiasms of individuals or small groups of developers, and the self-interest of voluntary association. Indeed, Archie, Gopher and WWW were developed as 'sidelines', and apparently came to compete for resources with their authors' 'real' jobs. This cooperative precompetitive endeavour continues through IETF working groups and elsewhere. The rapid continuing development of WWW and its related technologies owes much to this spirit.
	Academic and research infrastructure. Much of the above work is actually directly or indirectly publicly funded. However, the development of 'tools' is also explicitly identified for support, as they are seen to support education and research. For example: the NSF funds CNIDR in the US; it is likely that development work will be funded under many of the areas of the EU Fourth Framework Programme where RADAR systems have been identified as of strategic importance; through various other national and international funding initiatives (as in NordInfo support for the WAIS/WWW work described above). In the UK, a recent review of library provision in higher education recommended the expenditure of a significant amount of money to improve resource discovery systems (Libraries, 1993).
	Commercial. Several of the tool developers have commercialised their operations and are trying to position themselves to support the variety of emerging distributed information services. It is anticipated that many of the commercial services on the networks will want to offer services using the tools and techniques with which their prospective users are familiar. The developers of Archie have formed Bunyip Information Systems; WAIS Inc. has been created by the creators of WAIS and a company has been formed by the developers of Mosaic. The developers of Gopher have not moved in this direction but have introduced a licensing scheme for commercial users. At the same time a range of commercial products is appearing based on public domain code, adding value, and packaging services for particular communities of use.
One can see, then, at each of these three levels - network infrastructure; information resources; and resource discovery and access systems - a similar copresence of these latter three successively emerging orientations (community, academic and research, business). Developments at each level are being funded in a variety of ways, but will differ depending on national or regional characteristics. 
Indications are that the commercial component will grow rapidly. This view is supported by an interesting study into Internet growth rates by Michael Schwartz and John Quarterman (Schwartz and Quarterman, 1993). They note:
There are two conflicting trends in the development of Internet service infrastructure. Because the number of commercial institutions with connections are growing rapidly and tend to make significant use of distancing mechanisms, the Internet service infrastructure as we currently know it (i.e., free, publicly accessible network services) will likely be supported by a decreasing proportion of Internet sites, comprised primarily of non-profit, government, and academic institutions. At the same time, once the technology and market for commercial, for-fee services is firmly established in the Internet, an explosion in new types of services will most likely take place.
Sustainable resource discovery services
What is the current situation within the schema developed here?
	Community. Standardisation and consensus building is proceeding through several channels, notably Internet Engineering Task Force working groups, and the library community. In the meantime a range of experimental and prototypical systems exist (e.g. ALIWEB, Netfind, etc.) which provide useful services, and are supported by voluntary or research initiatives.
	Academic and research infrastructure. Various organisations are recognising the need to develop organised, sustainable access. Examples are the InfoServices Project, and the proposals for a Network Information Centre put forward by a working group of the Council of Australian University Librarians (Mays et al, 1993). Again, it is proposed that more infrastructural work will be taken up within research programs of the Fourth Framework Programme of the EU, the Libraries Initiative in the UK, as well as elsewhere. A Nordic Forum for Networked Information has been set up under the auspices of Nordinfo which will foster a range of activities in support of the creation and use of network resources.
	Commercial. There is a clear market for effective discovery services, as evidenced by the number of print guides which have appeared. A number of 'shop-window' services are available, where organisations offer a platform for promotional or product data. As in print, it will become possible to register resource descriptions in a number of outlets, some of which may levy charges.
Future services will be various. It is unlikely that a global monolithic service will develop. It also seems unlikely that global and 'free' services typical of phase three will be the model (Veronica is a current example of such an approach). This is not to say the technologies described here, or some other version of them, will not continue to be used. But, the resource discovery components currently being engineered will become the platform for resource discovery services, based on particular funding and user contexts. The current case of Bunyip Information Systems is interesting. Bunyip is a technology developer - they are the originators of Archie. Bunyip Information Systems supports a number of replicated Archie servers, and charges the service providers for their use. Some of these are private servers; some are made 'freely' available on the Internet. They provide similar services but to different communities of users. However Bunyip are also developing services based on other technologies. They are currently working on enhanced services which consolidate ftp and gopher metadata, and which harvest IAFA templates for richer indexing. Bunyip does not create the data: it is collected from servers worldwide; they provide a systems framework to exploit it and seek a return on that added value. In turn, one might see, for example, a national academic resource discovery service 'take' the Bunyip offering and integrate it into a portfolio of services. In the next few years, an industry of technology, systems and service providers is likely to develop, who share some basic approaches but add value in ways particular to their client base. Some of this effort will be supported through various types of R&D funding, some through continued commercialisation.
Given the current situation in the UK, and other European countries, systemic or infrastructural development within the public sector is unlikely to happen without central involvement, and it would seem appropriate to begin to arrange activities along national lines, however that is internally organised, with appropriate international links. At the same time international communities of interest will develop around particular subject interests (e.g. biologists, mathematicians,...). There is now some coordination at the level of standards and technology, but it needs to move out into coordinated services. There is some preliminary activity, but it is largely based on existing tools, and subject to the disadvantages outlined in Section 1. For example, there has been some activity, initiated within the European Gopher community, to establish National Entry Point Administrators in each country, which would carry out a range of organisational activity (e.g. registration of resources; organisation into geographical, subject and type of service trees; collect Veronica or other indexing data; provide a point of contact for software and advice; and so on) (Dempsey, 1993a). However, these are not consistently funded or organised. For example, UKOLN runs the Gopher NEPA for the UK, but provides only an undifferentiated list of servers <URL:gopher://ukoln.bath.ac.uk/11/UK_Gopher_Servers>. There is rather more activity within the Netherlands where Dutch Campus Wide Information Service administrators have taken a coordinated approach to the design and development of the NEP. There are guidelines for the registration and categorisation of services, and a number of other initiatives are underway (van der Werf, 1994b). 
In conclusion, technical and organisational frameworks for sustainable resource discovery are now the subject of investigation. Some of this work has been described in this paper. It is recognised that without such services investment in networks and information services is not as effective as it should be. However, no clear pattern of future provision has emerged. A recent UK report recognised this and recommended that a Network Information Development Agency be set up, charged with providing quality National Entry Point and registration services, coordination, international liaison, and the exploration of an effective infrastructure (ANIR, 1994). Other initiatives have been noted. The library community should recognise that it is well placed to play an important role in the design and delivery of such services in this important construction phase, and that the linking of such services with library resource discovery services is highly desirable. Libraries have stability and longevity, as well as a well-understood role and lines of funding which suit them to become stake-holders in this emerging environment.

Acknowledgements
I would like to thank staff at Lund University, the Royal Library, The Netherlands, and the Danish Technical Library for sharing their experiences with me, especially Anders Ardö, Traugott Koch, Titia van der Werf, and Mogens Sandfaer. I would also like to thank the BLR&DD for supporting this study. Readers will have noticed obvious debts, and I hope these are all recorded in the references. Writings of Lynch and Weider have been especially influential, though they of course are not responsible for the uses to which their work has been put. While preparing this paper I contributed to the report of the Access to Network Information Resources Working Group of the Information Services Sub-Committee of the Joint Information Systems Committee of the UK Higher Education Funding Councils, and was one of the small team preparing the draft Libraries Work Plan within the context of the EU's Fourth Framework Programme for Research and Technological Development. For this reason, there may be some textual resemblance between parts of those documents and parts of this paper.
I would also like to thank Peter Stone, John Lindsay, Titia van der Werf and Traugott Koch, and Tony Barry, for helpful comments on earlier drafts.
UKOLN is jointly funded by BLR&DD and the Joint Information Systems Committee of the Higher Education Funding Councils in the UK. Any opinions expressed here are my own.
References
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Dempsey, Lorcan. Research networks and academic information services: towards an academic information infrastructure: Part 1. Journal of Information Networking, 1(1), 1993, pp.1-27.
(Dempsey, 1994)
Dempsey, Lorcan. Distributed library and information systems: the significance of Z39.50. Managing Information, 1(6), pp. 41-43.
(Dempsey et al, 1993)
Dempsey, Lorcan and Mumford, Ann and Tuck, Bill.  Standards of relevance to networked library services. In: Libraries and IT: working papers of the Information Technology Sub-committee of the HEFCs' Libraries Review. Bath: UKOLN, 1993, pp. 131-155
(Deutsch and Emtage)
Deutsch, Peter and Emtage, Alan. Publishing information on the Internet with Anonymous ftp. Internet draft. (Work in progress) <URL:ftp://nic.nordu.net/internet-drafts/draft-ietf-iafa-publishing-00.txt>
(This version has now been withdrawn)
(Foster, 1994)
Foster, Jill (ed.). A status report on networked information retrieval: tools and groups.  March 1994. Internet draft. (Work in progress) <URL:ftp://nic.nordu.net/internet-drafts/draft-ietf-nir-status-report-03.txt>
(Hardy and Schwartz, 1994)
Hardy, Darren and Schwartz, Michael. Customized information extraction as a basis for resource discovery. March 1994. Department of Computer Science, University of Colorado, Boulder, Technical report CU-CS-707-94. 
(Israelson, 1992)
Israelson, Ann-Sofi, and Petrilli, Achille, and Sandfaer, Mogens and Schwarz, Stephan. High-tech information network in high energy physics. In: Wide-area networks in libraries: technology, applications, and trends. Westport CT: Meckler, 1992, pp.89-110.
(Koch, 1994)
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(also available in HTML format: <URL:http://www.ub2.lu.se/nordic_w4.html>)
(Koster, [1994])
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(Law, 1994)
Law, Derek. The development of a national policy for dataset provision in the UK: a historical perspective. Journal of Information Networking, 1(2), 1994, pp. 103-116.
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Schwartz, Michael F. Internet resource discovery at the University of Colorado. Computer, September 1993, pp.25-34.
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(TEI, 1994)
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(Treloar, 1994)
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van der Werf, Titia. Personal communication, 19 July, 1994.
(Weider, 1994a)
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Sidebar 1: Acronyms
ALIWEB	Archie Like Indexing in the Web
BUBL	Bulletin Board for Libraries
CERN	European Laboratory for Particle Physics
CGI	Common Gateway Interface
CNI	Coalition for Networked Information
CNIDR	Centre for Network Information Discovery and Retrieval
FTP	File Transfer Protocol
HTML	Hypertext Markup Language
HTTP	HyperText Transfer Protocol
IAFA	Internet Anonymous Ftp Archives (working group of the IETF)
IETF	Internet Engineering Task Force
ILL	Interlibrary Loan/Lending
ISBN	International Standard Bibliographic Number
ISO	International Organization for Standardization
MARBI	American Library Association Committee on Representation in Machine-readable form of Bibliographic Information
MARC	Machine Readable Cataloguing
MIME	Multipurpose Internet Mail Extensions
NCSA	National Center for Supercomputing Applications
NEP(A)	National Entry Point (Administrator)
NIDR	Network Information Discovery and Retrieval
NISS	National Information on Software and Services
OCLC	Online Computer Library Center
OPAC	Online Public Access Catalogue
Pica	Projet geIntegreerde Catalogus Automisering
RADAR	Resource Access Discovery and Retrieval
SGML	Standard Generalised Markup Language
SR	Search and Retrieve
TEI	Text Encoding Initiative
URC	Uniform Resource Characteristics
URI	Uniform Resource Identifier
URL	Uniform Resource Locator
URN	Uniform Resource Name
WAIS	Wide Area Information Server
WWW	World Wide Web

Sidebar 2: URLs

The URL has two parts. The first part is the access method or protocol, as in: 

	gopher://gopher.well.sf.ca.us/  
	http://www.uky.edu/Artsource/artsource.html

 the second is the actual location or address of the service, as in:

	gopher://gopher.well.sf.ca.us/ 
	http://www.uky.edu/Artsource/artsource.html

URLs are increasingly being used to share details about how to access resources and in citations.

Sidebar 3:  Proposed architecture of an integrated information service
      _____________________________________________
     |         |        |       |        |         |
     |  Gopher |  WAIS  |  WWW  | Archie | Others .|
     |         |        |       |        |         |
     |_________|________|_______|________|_________|
          |                                |
          |                       _________|____________
          |                      |                      |
          |                      | Resource Discovery   |
          |                      |  System (perhaps     |
          |                      |  based on whois++)   |
          |                      |______________________|
          |                                |      
          |                                |
     _____|________________________________|____
    |                                           |
    | Uniform resource name to uniform resource |
    | locator mapping system (perhaps based on  |
    | whois++ or X.500)                         |
    |___________________________________________|
                        |
                        |
        ________________|______________________________________
        |                  |                 |                 |
  ______|______     _______|_____      ______|______     ______|______
 | Transponder |   | Transponder |    | Transponder |   | Transponder |
 |_____________|   |_____________|    |_____________|   |_____________|
 |             |   |             |    |             |   |             |
 |  Resource   |   |  Resource   |    |  Resource   |   |  Resource   |
 |             |   |             |    |             |   |             |
 |             |   |             |    |             |   |             |
 |_____________|   |_____________|    |_____________|   |_____________|

This schema has been proposed within the Integration of Internet Information Resources Working Group of the IETF as a 'vision' of how services might be integrated and developed (Weider and Deutsch, 1994a).
Four levels are proposed:
1.	Resources themselves. Each resource should have a Uniform Resource Name.
2.	A directory service (undefined) which resolves names into locators (a resource may have several locations).
3.	A resource discovery system (undefined). This would be a searchable database of resource descriptions. This would allow the user (or user agent) to discover the URNs of relevant resources. (Of course, if a name or location is already known, the discovery and name to locator services would not be required). WHOIS++ is a lightweight directory service which is currently being developed; it is not yet widely deployed but is seen by some as a substitute for slowly developing X.500 services.
4.	Access and delivery tools. 

Sidebar 4 : NISS/BUBL subject access
A cooperative approach to the 'classification' and description of network resources is being taken by the BUBL Information Service and NISS in the UK. They have recruited a team of volunteers with specific subject interests who identify and, in some cases, describe resources in their subject area. A template for the descriptions has been developed be NISS, and they are using UDC (Universal Decimal Classification) to classify resources by subject. The project is in early stages and how to present the services to users is under discussion. BUBL will list resources within its subject tree (<URL:http://www.bubl.bath.ac.uk/BUBL/Tree.html). NISS is investigating making the descriptions available as a searchable database, which would be accessible for NISS and BUBL users. Access will be via WWW, and result sets returned as a set of links to resources.
Source: Personal communication from Eddie Zedlewski, NISS Manager and Dennis Nicholson, Strathclyde University, BUBL Coordinator.

Sidebar 5 : the Nordic WAIS/World Wide Web project
This is a project funded by NordInfo and involving the Danish Technical Library and Lund University Library, UB2 (Ardö, 1994). It is a year long, stretching from Summer 1993 to Summer 1994, and represents a natural extension of each libraries' interests. Ardö and Koch, at Lund, have been pursuing several related projects using WAIS and other tools (Ardö et al, 1993; Koch, 1994). DTB have an interest in WWW, and close links with CERN (Israelson, 1992).
The project builds on work experiences gained with WAIS and WWW, and has a double focus: to improve searching capability by some imaginative processing of existing metadata extracted from resources, and to build better links between WWW and WAIS. Elements of the work are briefly described here
Automatic indexing and classification of WAIS sources
	Harvesting of WAIS metadata. Descriptive information is collected from WAIS source files, and from some other known sources. The process is as automated as possible, and much of the data is automatically extracted by a program which routinely 'walks through' various known sources.
	A list of keywords is derived from the descriptions, and augmented with subject terms from other sources, such as other subject listings. Keywords are weighted depending on the perceived importance of where they originate; for example words from the subject field of the WAIS source descriptions have a relatively high weighting.
	These are matched against words derived from partial UDC schedules; principally terms from broader levels throughout all subject areas. (UDC, Universal Decimal Classification, is a classification system used in some libraries. The project uses the UDC English Medium Edition).
	Based on matches, this results in a series of suggested classifications
	The final classification is based on the accumulated weights for each classification. In this way a resource may have several classification numbers associated with it. (There is a cut-off point below which classification numbers are not selected).
	The WAIS databases are then organised into a subject tree based on UDC. This is accessible through both WWW and Gopher.
Of course the results depend on a number of factors: assigned weights, matching algorithms, the depth and range of UDC terms used. There is occasional false classification, and failure to make any match because of the terseness or absence of descriptions. These issues are all for experiment. Importantly, the developers note that results depend heavily on the quality of the original metadata the WAIS source files. This approch uses UDC, but is not tied to it: other classification schemes could be used.
Orientation tool for WAIS
The subject tree created in the above way can be used to construct a data structure corresponding to a 'WAIS question'. This consists of a list of databases together with empty fields for search terms and lists. This can in turn be used by a client as a preselected set of WAIS databases for a specific subject.
The subject tree and the 'WAIS' questions are made available to WWW users through the WWW to WAIS gateway which the team have also developed. This uses the CGI specification and the forms feature of Mosaic. URLs for the service are gopher://gopher.ub2.lu.se/1/allWAIS/experiment and http://www.ub2.lu.se/autoclass.html
Building a gateway from WAIS to WWW
The project aims to create a database of WWW links, and to index these in a WAIS database. Selected retrievals from the database starts up a WWW client. The project is one of a number looking at approaches to indexing the Web. Currently, they are indexing Nordic resources in one database per country. An interesting aspect of the project is the question of what, in the absence of consistent resource descriptions, ought to be indexed. The team is experimenting to decide which combination of four options to use: the sentence in which the link occurs; the heading of the page which contains the link (not always present); the entire page (volume!); the filename part of the link (not always relevant). The project is also experimenting with possible architectures, to see what combination of centralised, distributed and local (to the WWW server) effort is appropriate at various stages: indexing, collection and organisation of metadata, and searching. Options include: automatic extraction of metadata into a central index; automatic collection of locally created indexes into a central server; partition of the resource space and construction of a central index for each part, which can be searched singly or together. All Nordic WWW servers are automatically polled. The URL of a test service is http://www.ub2.lu.se/wwwindex.html. This allows one or more of the databases (one for each Nordic country) to be searched together and presents a consolidated result to the user. Further databases, based on the indexing of resources in other countries, may be added in the future. This service is based on the WWW to WAIS gateway also developed within the project.
Improve the gateway from WWW to WAIS
This part of the project aims to enhance the functionality of WAIS available through the existing WWW to WAIS gateway at CERN. The improved gateway will allow several databases to be searched at once, as well as the use of relevance feedback, and is being used as described in the last section. 

The project is also looking at the improvement of the WWW gateway to the ALIS library system; see Sidebar:7  for some discussion of this.

(Sources: cited references, personal communications from Anders Ardö, Traugott Koch, Mogens Sandfaer; some of the text has been edited from a private communication from Traugott Koch of Lund University.)

Sidebar 6 : InfoServices - a national information service
In a joint initiative, the Royal Library (KB) and SURFnet in The Netherlands have set up a project called InfoServices. It is interesting because it arose from a decision by SURFnet that its own information services could be improved, and that it was appropriate to do this in conjunction with a library partner. SURFnet bought a host machine, which is supported by the Computer Centre at the University of Utrecht. There are two and a half full time equivalent members of staff employed on the project and the costs are shared equally between KB and SURFnet. This arrangement acknowledges a joint recognition of a convergence of interests, and, for the moment, the appropriate division of responsibilities.
InfoServices is one of a number of related initiatives in The Netherlands which are looking at how new electronic resources will be managed, and what the traditional links back into library services are.
The service does several things. It manages the dissemination of SURFnet information on the server, and in the process is trying to set standards for good practice in information management. In particular, it is hoped to provide a model for organisation of servers in the SURFDOC project, another initiative of SURFnet's, in which Dutch university libraries and computing centers are setting up document servers to make local technical, report and other literature available in a consistent way. IP has also an interest in providing organised access to Internet resources, and is experimenting with a subject approach to network resources, in which local subject experts identify resources of interest in their areas, which are then organised into a tree organised by the Dutch Basic Classification. They are taking over the organisation of the Dutch National Entry Point, located at the University of Groningen.
An interesting aspect of the service is its approach to the creation and distribution of metadata. Originally staff began to 'catalogue' files on the server along library lines, but it was soon realised that this was not sustainable, and data providers were asked to provide a description of the resource with any submitted files. (Only material judged of interest or of durable value by staff is actually mounted.) This description is stored alongside the file on the server where it can be inspected by the user. It was also decided to integrate these descriptions into the Pica database.
The project was concerned to adhere to emerging standards in this area. Accordingly, the descriptions are formatted according to the IAFA 'document' template. InfoServices participates in the experimental Bunyip service, where these descriptions of ftp files will be collected into an enhanced Archie service. The project developed a format for online resources based on the MARBI proposals, and Pica has implemented a format for online resources along these lines. The IAFA descriptions are enhanced to form the 'catalogue' records.
In this way, albeit on a still small scale, the project is building valuable experience along necessary integration paths. The documents will be accessible through RADAR systems based on the harvesting of the IAFA templates. They will also be accessible through traditional library access routes. Users can order the documents through the Pica interlibrary loan system, or they can access the document through the Gopher client integrated with the Pica library system. Currently this latter link is not automated. URLs are included in the records, just as shelf-marks occur in monograph records, but the Pica system does not interpret and act on the URL. Future directions here are being investigated, but for the moment Pica is concentrating resources on developing its 'managed information network' rather than looking to integrate RADAR services into its offerings. IP is one of the few European initiatives in this area to date, and its progress will be instructive.
Sources: Werf (1994) and personal communications from Titia van der Werf.

Sidebar 7 : Linking library servers and RADAR systems directly: some European examples
In several interesting cases, libraries have implemented gateways between their 'private' library servers and RADAR systems. Some examples are presented here. 
BIBSYS
BIBSYS is a national Norwegian shared cataloguing and automation system, which is a partner in the Nordic SR-Net project mentioned in Sidebar 9. BIBSYS have also developed gateways from Gopher and WWW to the BIBSYS server which understands a proprietary protocol. Users enter text strings through either the Gopher or WWW interface - they have to structure the queries in a form expected by the BIBSYS server. This has been done so that users can use the service in whatever mode fits their work and information seeking behaviour. This approach has the added advantage that users can save simply-structured text records to the client machine for subsequent use. The service has proved very popular with users. (To look at the service, URLs are gopher://gopher.bibsys.no and http://www.bibsys.no). Users also have access to holdings and availability information through this interface, and eligible users can request books from any library in the system.
This initiative is one strand only of a series of service offerings which make BIBSYS unusually and commendably 'open' in terms of Internet access. Facilities are in place to allow file transfer of records to a user's own machine by ftp, or to search and transfer records by e-mail.
Source: personal communication from Ole Husby, Bibsys.

Informatics Library, University of Oslo

This represents a very interesting example of an innovative service which provides library facilities within a WWW environment. The URL is http://www.ifi.uio.no/ifibib/ifibib_eng.html. A gateway has been constructed to the institution's  catalogue database. Dynamic hypertext linking between records in the catalogue is implemented. Access is also provided to the Bibsys service, mentioned above. 
Source: personal communication from Knut Hegna, Informatics Library

Danish Technical Library (DTB)
CERN and DTB both use the ALEPH library automation system, and have worked closely with the system developer in determining future interface requirements. Together they have been working towards implementing ALEPH in a client-server environment in which there are a variety of user access options. Users will access the system using either a WWW client, a SR/Z39.50 client or a proprietary ALEPH client. These talk respectively to a WWW server, a Z39.50 server and an ALEPH server, which all in turn interface to the OPAC search engine. These developments are so far experimental, but it is planned that ALEPH will exploit some of this work in future releases of the system.
Within the Nordic WAIS/WWW project discussed above work is now being carried out on enriching the WWW/ALEPH OPAC gateway, so that more of the OPAC's functionality is available through the WWW interface. Examples are a type of 'more like this' feature, where a user can request more items based on links between a selected item and relevant indexes, and the ability to display holdings and availability data as well as descriptive data. 
Source: Personal communication from Mogens Sandfaer, DTB, and Ardö et al, 1994.

Sidebar 8 : WWW to Z39.50 gateways
Chachra et al ([1994]) suggests that there are two current approaches to integrating access to Z39.50 servers WWW:
	combining a WWW server with a Z39.50 gateway
	combining a WWW client with Z39.50 URL support
Interestingly these correspond to the two approaches for integration of access methods identified above: the creation of gateways, and the deployment of a metadata propagation infrastructure.
In the first a gateway is implemented between a WWW server and a Z39.50 server. The WWW server passes the query to the Z39.50 server, and converts results to a HTML document presented by the client. (See the CNIDR gateway for an example: http://??). In the second, the browser interprets a Z39.50 URL and either calls a local Z39.50 client (which is the method VTLS is using to interface Mosaic to its Z39.50 client). A problem with this approach is that a standard Z39.50 URL has not yet been defined, so that a special 'fix' is currently used.

Sidebar 9 : Some European implementors of SR and Z39.50

IRIS. This is an Irish current awareness and document supply service. As part of the service users will be able to search the OPACs of six Irish libraries and to request items. The user interacts with a user application which hides the different OPAC interfaces and connection details and which provides integrated search and request functionality. The user application, developed by Fretwell-Downing, communicates with the OPAC servers through Z39.50. The project is supported by the  European Regional Development Fund through the Telematique Programme of the EU.

Nordic SR-Net. This is a project sponsored by NordInfo to link union catalogue organisations in Nordic countries, and to develop a consolidated bibliographic resource. Users should have transparent access to the various systems, and be able to easily transfer records between them. Participants include shared and union catalogue organisations in Norway, Sweden, Finland and Denmark. Iceland participates as an observer.

Project ION*. The Interlending OSI Network aims to link national interlending systems in the UK, The Netherlands and France using the ILL protocol (ISO 10160/1). One component of this initiative involves implementation of SR on the Viscount and Pica databases, to allow mutual lookup.

DBV-OSI. It is proposed to link several German regional Verbundsysteme and online host systems, again with the aim of presenting the user with transparent access to a consolidated resource for search and request of materials.

Socker*. This project is implementing SR client applications in various different environments. IME is integrating a client with its library system; UNI-C, the Danish academic computing and networking organisation, is implementing it within a standalone workstation application; FEK, a library computing organisation, is implementing it as a network 'information gateway' application, providing a network accessible client as part of a larger service.

Europagate* Danish, Irish and Spanish partners are implementing a gateway between SR and Z39.50.

Other projects. The British Library is implementing Z39.50 and SR server interfaces to its OPAC, with a view to participating in experimental international projects. This experience will feed into planning for incorporation into possible service offerings. Other organisations are implementing in various contexts: Pica, Karlsruhe University, ESA-IRS, Library system vendors (SLS, BLCMP, Fretwell-Downing...). Further projects will be funded as a result of the third call for proposals under the Libraries Action Plan of DGXIII. At the time of writing, proposals are still being evaluated.

* supported under the libraries' programme of DGXIII of the EU

.