Xcerpt and Xchange: Deductive languages for data retrieval and evolution on the web
François Bry, Paula-Lavinia Pătrânjan, Sebastian Schaffert · 2004
this article is a general purpose language that can query any kind of XML data, i.e. standard Web as well as Semantic Web data, and at the same time provides advanced reasoning capabilities. It could thus serve to implement a wide range of di#erent reasoning formalisms. Likewise, the maintenance and evolution of data on the (Semantic) Web is necessary: the Web is a "living organism" whose dynamic character requires languages for specifying its evolution. This requirement regards not only updating data from Web resources, but also the propagation of changes on the Web. These issues have not received much attention so far, existing update languages (like XML-RL Update Language [2]) and reactive languages [3] developed for XML data o#er the possibility to execute just simple update operations and, moreover, important features needed for propagation of updates on the Web are still missing. The language XChange also presented in this article builds upon the query language Xcerpt and provides advanced, Web-specific capabilities, such as propagation of changes on the Web (change) and event-based communication between Web sites (exchange), as needed for agent communication and Web services