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Metadata in Digital Libraries, DELOS meeting, Riga, Latvia, 16 April 2003

Exercise 3: Exploring the DCMI metadata schemas registry


This exercise introduces the DCMI metadata schemas registry as an application which allows you to explore the Dublin Core metadata vocabulary.

Task 1: Setting Preferences

View the registry front page in your Web browser. <URL:>.

The front page allows you to set language preferences for both the user interface and the content (separately if you wish!). Choose your preferences and click Submit, then click Search.

Task 2 : Browse the DC Metadata Elements

Select "Elements" in the "Display: " drop-down list, and click Submit.

The registry displays a list of the Elements recommended by DCMI. (Note that a sixteenth Element "audience" was recently added to the vocabulary).

From the summary list, you can follow links to the full description of each Element.

Task 3 : Browse the DC Metadata Element Refinements

Select "Element Refinements" in the "Display: " drop-down list, and click Submit.

The registry should display a list of the Element Refinements recommended by DCMI.

An Element Refinement is a property of a resource which shares the meaning of a particular DCMI Element but with narrower semantics. In some application environments (notably HTML-based encodings), Element Refinements are used together with Elements in the manner of natural-language "qualifiers" (i.e., adjectives). However, since Element Refinements are properties of a resource (like Elements), Element Refinements can alternatively be used in metadata records independently of the properties they refine. In DCMI practice, an Element Refinement refines just one parent DCMI property.

- DCMI Grammatical Principles

The description of each Element Refinement includes a "Subproperty Of" relationship to an Element.

Browsing by "Properties" should generate a list which includes both Elements and Element Refinements.

Task 4 : Browse the DCMI recommended Encoding Schemes

Select "Vocabulary and Encoding Schemes" in the "Display: " drop-down list, and click Submit.

An Encoding Scheme provides contextual information or parsing rules that aid in the interpretation of a term value. Such contextual information may take the form of controlled vocabularies, formal notations, or parsing rules. If an Encoding Scheme is not understood by a client or agent, the value may still be useful to a human reader. There are two types of Encoding Scheme:

  • Vocabulary Encoding Schemes indicate that the value is a term from a controlled vocabulary, such as the value "China - History" from the Library of Congress Subject Headings.
  • Syntax Encoding Schemes indicate that the value is a string formatted in accordance with a formal notation, such as "2000-01-01" as the standard expression of a date.

- DCMI Grammatical Principles

In most cases, DCMI registers only the Encoding Scheme as a unit, and not the individual terms/values which might make up a controlled vocabulary.

Task 5 : (for the adventurous!) Browse the DCMI "RDF Schemas"

DCMI publishes machine-processable description of its vocabularies using the RDF Vocabulary Description Language (RDF Schema). The registry application allows you to query and navigate the data published in those schemas: the registry can be seen as a "Semantic Web" application, albeit one which operates on a small and controlled set of input data.

If you wish to view the DCMI schemas, the RDF/XML files are available at:

The W3C online RDF Validator will generate a view of the data in the schemas as RDF triples and as graphs:

The graphs will appear very complex! The purpose of this exercise is simply to emphasise that the schemas make use of the same simple RDF model of Subject-Predicate-Object as the simple DC metadata we saw generated by DC-dot in exercise 1.