Alterations

The final version of our testprogram resembles the design as stated in the previous section rather closely. Since the testing started very early in the development cycle, I did find some problems relating to the design of the system rather quickly. In the introduction I mentioned the need to adhere to standards for allowing interoperability between software systems. Especially the communication between peers should be open and standards-based as much as possible. One can argue that relational database management systems based on the SQL query language form a standard, but unfortunately SQL is rarely used as a communication protocol on the internet. The most prominent change from the design stems from this insight. More and more software systems use XML(13) as the grammar for their communication and many development kits exist to accommodate the use of XML. Because of this, I've decided early in the development cycle to focus on using XML and other webstandards based on this, such as RDF, as much as possible.

Using XML and RDF doesn't automatically rule out the use of a rDBMS as back-end data repository. I did remove it, however, in favour of a direct XML connection to speed up the development process.

Another change having to do with the use of XML has to do with the user interface module. The main standard on the internet of showing data is the hypertext markup language, which itself is based the XML grammar. The fact that our data is already encoded using XML gives us the opportunity to quickly create user output in a format recognized by any webbrowser. The interface to the data indexing part of the application is still developed as a $Windows^{tm}$ application. Ideally, administration and file-addition should also be made possible using webtechnology. The necessary added cost of implementing security has kept me from adding this functionality in the current program, however.

The resulting application thus consists of the four modules as detailed, but with the added webinterface used for querying the network.