Raising Awareness

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An Introduction to Web APIs

What is a Web API?

API stands for 'application programming interface'. An API is the interface that a computer system, computer library or application provides to allow requests for services to be made of it by other programs and/or to allow data to be exchanged between them. A Web API is the Web version of this interface [1]. It comprises of documented code and is effectively a way to plug one Web site or Web service into another.

Recently many Web sites have exposed APIs and made them available to external developers. The term Open API is often used to describe the technologies that allow this interaction.

What Can Web APIs be Used For?

Developers can use Web APIs to build tools for the host Web site and enrich their own applications with useful functions from third parties. This provides several advantages:

For the host site:
The advantage of exposing ones APIs is that developers will create new features and applications for free. These applications will then drive traffic to the site.
For the developer:
Creating applications allows developers to promote their own work on higher profile Web site and build on existing work. Their own Web site can then benefit from the traffic. Developers can also mix and match information data from different sources to creation a solution to a problem.

Getting Started

To access a Web API developers will normally need to register for a (often free) account and get a private key which is required for calling server functions. Each API has its own terms and conditions that will need to be followed, for example there may be limitations on the number of calls to the site per day.

Someone with programming experience could build an application using available APIs fairly quickly but there are now a number of good development tools available such as Yahoo Pipes [2] that allow those with little programming experience to begin developing simple Web applications.

Examples of Web APIs

Many commercial companies now expose their APIs including Facebook, Yahoo, Google, Google Maps, Flickr and YouTube.

There are a number of API directories including Programmable Web API directory [3], Webmashup [4] and the WebAPI Directory [5]. A list of useful APIs for library services on the blog [6].

Opportunities and Challenges

Web APIs are likely to become increasingly important and more organisations will want to make their own APIs available as a way to raise their profile and add value. Amazon recently released graphs that show the growth in bandwidth being consumed by their customers via their various Web services. More activity network activity takes place in this way than through all their other Web sites combined. Uptake of data and software by third party Web applications through Machine to Machine (M2M) interfaces is becoming more important than user interfaces.

This move of focus means that more work will be done to make sure that APIs that deigned in an appropriate and compatible manner. There will also be significant challenges relating to how organisations use the data available, which may be personal and sensitive.


  1. Wikipedia: API, Wikipedia, <>
  2. Yahoo Pipes, Yahoo!, <>
  3. Programmable Web API directory, <>
  4. Webmashup,, <>
  5. WebAPI Directory,, <>
  6. Services/APIs/Systems/Technology/Data that we could use, Mashed Library,, <>
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