Web APIs

Web APIs are sexier that desktop APIs. Having an API allows the external developers to access your data or your services in a smart way. They can they use your data or services in ways you would not imagine.

Currently it is very popular to use the data with mapping APIs. At the moment the Google Maps have the best and most detailed images of Australia. Microsoft competes with Virtual Earth, they have good images, good maps, but a very restrictive licensing. Yahoo! Maps has also good images and also gives a choice of Flash or JavaScript. They also provide an option of a static image. The downside of Yahoo! Maps is the lack of mapping information.

Another popular category of APIs is Search. Search APIs can provide cache access, spell-checking, content analysis and much more. Amazon's API offers search on prices, images, customer reviews and affiliate sales.

A good resource for Web APIs is ProgrammableWeb, which acts as an encyclopedia of available APIs and how people use them.

Mashups are novel UI that enhance your data, e. g. by combining your local data with mapping information. Chicagocrime.org – one of the first map mashups was built prior to Google’s API being made public. It’s not all about maps – TagTV, Viral Video Chart, BlueOrganizer, Salesforce Adwords.

There are two general types of APIs: interfaces (maps) and data types (the rest). For example Google Maps are very simple to include; just drop in the script, add four lines of JavaScript and you are done. The other APIs are simply a request to a web resource via HTTP. XML is often used to return the result, though JSON is becoming more popular. These can also be called directly from JavaScript using the XMLHttpRequest object.

The current limitations several. You are limited to the functionality that the provider makes available, unless you screen scrape. There are also concerns with automated collection of personal data, licenses and the changes in terms of use (what will you do if Google Maps is no longer available). We also need to standardize. There are some APIs available that abstract the mapping API access and allow you to switch between Google Maps, Yahoo Maps, etc. Cross domain AJAX is also a security risk. Images, CSS and JavaScript can be loaded from other damains, but HTML or XML can not. A workaround could a proxy server, but this could be a bottleneck if not cached. JSON-P is another alternative, currently supports GET requests, but fails silently if you get the API URL wrong.

In the future we can see ContextAgnosticXmlHttpRequest, enhanced JSON – JSONRequest. Web APIs are all about work we do not have to do. So open your data, offer an API, let the others do the work!