| Abstract |
Information systems such as organizational memories, vertical aggregators, infomediaries, etc. are expected to play a central role in the 21st-century economy by enabling the development and maintenance of specific communities of interest (e.g., enterprise, professional, trading) on corporate intranets or the Web. Such Community Web Portals essentially provide the means to select, classify and access, in a semantically meaningful and ubiquitous way various information resources (e.g., sites, documents, data) for diverse target audiences (corporate, inter-enterprise, e-marketplace, etc.). Yet, in commercial software for deploying Community Portals, querying is still limited to full-text (or attribute-value) retrieval and more advanced information-seeking needs require navigational access. Furthermore, recent Web standards for describing resources (see the W3C Metadata Activity: RDF/ RDF Schema) are completely ignored. Moreover, standard (relational or object) databases are too rigid for capturing the peculiarities of RDF descriptions and schemas. Motivated by the above issues, we propose a new data model and a query language for RDF descriptions and schemas. Our language, called RQL, relies on a formal graph model, that captures the RDF modeling primitives, also providing a richer type system, and permits the interpretation of RDF descriptions by means of one or more schemas. In this context, RQL adapts the functionality of semistructured query languages to the peculiarities of RDF but also extends this functionality in order to query RDF schemas. The novelty of RQL lies in its ability to smoothly switch between schema and data querying while exploiting - in a transparent way - the taxonomies of labels and multiple classification of resources.
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Μια δηλωτική γλώσσα επερώτησης μεταδεδομένων RDF για πύλες Κοινοτήτων Διαδικτύου
