This assignment deals with the easiest Web-based service next to pure file retrieval: HTTP content negotiation. By configuring a Web server appropriately, users can be served with documents that match their language preference. This is much better than the usual please choose your language way of having the user answer this question for each Web site he is visiting.

As a simple front-end for a Web-based service, an HTML form should be designed which can be used to enter a simple query for a set of bibliographic references. The HTML form should later serve as a front end for accessing a real service, but in this assignment, only the form should be designed so that it enables users to enter their query data.

Now the query data entered by a user through the HTML form should be submitted to an HTTP Web service, and the results should be presented to the user. This way, a very simple bibliography search tool can be implemented. The glue for embedding the query data to the Web service is PHP code.

The bibliography service has now been extended to provide the information in XML. In this assignment, PHP5's SimpleXML implementation is used to extract information from the XML. Now it becomes possible to build a service which not only is build around the data provided by the query service, but selectively reuses parts of it to provide links to related information provided by 3rd party services.