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http://rewerse.net |
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Enabling more "meaningful" access to Web and Semantic Web data by integrating reasoning capabilities in a Web query and transformation language. Querying, i.e., the efficient and effective access to data, is one of the most essential enabling technologies for any information system. In the Web context, reasoning capabilities enhance traditional search and access technologies to be able to cope with heterogeneous, incomplete, and often even inconsistent information.
Access to Web data has ecome an integral part of many applications and services. In the past, such data has usually been accessed through human-tailored HTML interfaces. Nowadays, rich client interfaces in desktop applications or, increasingly, in browser-based clients ease data access and allow more complex client processing based on XML or RDF data retrieved throughWeb service interfaces. Convenient specifications of the data processing on the client and flexible, expressive service interfaces for data access become essential in this context. Web query languages such as XQuery, XSLT, SPARQL, or Xcerpt have been tailored specifically for such a setting: declarative and efficient access and processing of Web data. Xcerpt stands apart among these languages by its versatility, i.e., its ability to access not just one Web format but many. In this demonstration, two aspects of Xcerpt are illustrated in detail: The first part of the demonstration focuses on Xcerpt’s pattern matching constructs and rules to enable effective and versatile data access. It uses a concrete practical use case from bibliography management to illustrate these language features. Xcerpt’s visual companion language visXcerpt is used to provide an intuitive interface to both data and queries. The second part of the demonstration shows recent advancements in Xcerpt’s implementation focusing on experimental evaluation of recent complexity results and optimization techniques, as well as scalability over a number of usage scenarios and input sizes.
Detailed demo description and screencasts: http://queryware.com/xcerpt/cast/
(Note: Apple Quicktime is necessary for playing back the embedded screencasts)
Demo: http://rewerse.net/I4/software/Xcerpt/
Contact: Sacha Berger, Francois Bry, Tim Furche, Benedikt Linse (Munich)
dlvhex is the name of a prototype application for computing the models of so-called HEX-programs, which are an extension of Answer-Set Programs towards integration of external computation sources.
At the beginning of this project, we were pondering about how to contribute to the current efforts of shaping the Semantic Web. People seem to have agreed on the Ontology Layer with OWL as its prominent specification language. The next step is to add rules in order to have powerful and sophisticated inference mechanisms on top of ontologies. This is were we saw the opportunity of introducing Answer Set Programming (ASP) to the Semantic Web development - believing in the benefits of a fully declarative, nonmonotonic logic programming semantics.
Our first goal was to extend ASP towards an interface to Description Logics, which are the theoretical foundation of ontology languages like OWL. We developed so called dl-programs, which allow for a bidirectional flow of information between an answer-set program and a DL knowledge base by a novel type of atoms.
Motivated by the need to interoperate with a broader set of external computation sources and the observation, that for meta-reasoning in the context of the Semantic Web, no adequate support is available in ASP to date, we extended the dl-program approach to HEX-programs, that is, higher-order logic programs (which accommodate meta-reasoning through higher-order atoms) with external atoms for software interoperability. Intuitively, a higher-order atom allows to quantify values over predicate names, and to freely exchange predicate symbols with constant symbols, like in the rule
An external atom facilitates to determine the truth value of an atom through an external source of computation. For instance, the rule
computes the predicate reached taking values from the predicate &reach, which computes via &reach[edge, a] all the reachable nodes in the graph edge from node a, delegating this task to an external computation source (e.g., an external deduction system, an execution library, etc.).
Detailed demo description: http://con.fusion.at/dlvhex/
Contact: Roman Schindlauer (Vienna)
Further Information on I4 website
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