Development of an object oriented framework for design andimplementation of database powered distributed Web applications with theDEMETER project as a real-life example

摘要

We develop an object-oriented framework for generatingInternet-distributed database-powered World Wide Web applications. Werely on the proven technology of standard relational databases, but ourtools are designed from scratch, aimed especially towards the needs ofthe Web with low-bandwidth connections. We use a state machine model forthe design and implementation of control elements for Web pages withpure HTML. Sufficient complexity within the user interface and powerfuldatabase interaction can be achieved without Java, JavaScript orActive-X, even with more than one concurrent session at once. Based onthe state machine model, our design language models the applicationfunctionality strictly separated from layout and presentation. Thisapproach makes it independent from future changes to HTML, and we caneven give an application more than one layout without changing thefunctional structure, e.g. to satisfy users' needs. The object-orientedstructure of the design tools makes the framework extensible. With thistechnique, a database-powered Web application has been implementedsuccessfully: a Europe-wide product marketing system for rural areas,which is currently in the pilot phase. This system has been constructedunder the DEMETER (Distance Education, MultimEdia Teleservices andtElework for farmeRs) project, funded by the European Commission underthe 4th Framework programme TURA (Telematics for Urban and and RuralAreas)