Web and Semantic Web Query Languages

A number of techniques have been developed to facilitate powerful data retrieval on the Web and Semantic Web. Three categories of Web query languages can be distinguished, according to the format of the data they can retrieve: XML, RDF and Topic Maps. This article introduces the spectrum of languages falling into these categories and summarises their salient aspects. The languages are introduced using common sample data and query types. Key aspects of the query languages considered are stressed in a conclusion

DEDUCTIVE EXTENSION OF A RELATIONAL DATABASE SYSTEM

Logic based knowledge processing systems such as PROLOG based expert systems have shown obvious drawbacks in performing conventional database tasks. Knowledge processing by deduction on a large set of given facts can be better performed by a deductive database system based on Horn logic and relational database theory. A concept is presented to extend an existing relational database system to make feasible the deduction of intensional data from a given extensional database. The deductive extension provides an extended view mechanism and the integration of integn\u27ly constraints and leads to an enhanced quety mechanism. Thus, the conventional database becomes more expressive, shows a higher degree of consistency, and is evaluated more efficiently