Thursday, October 19, 2006

Semantic Web Client Library 

Semantic Web Client Library: "There is a recent tendency in the Semantic Web community to stress the Web aspect of the Semantic Web, meaning that the Semantic Web is increasingly understood as a single, global information space consisting of interlinked RDF data.

This tendency is carried by the revival of ideas around interlinking data on the Semantic Web: Current W3C efforts stress the fact that URI references should be dereference-able (W3C working draft on Best Practice Recipes for Publishing RDF Vocabularies). There is a nice memo by Tim Berners-Lee about the role of links on the Semantic Web (Berners-Lee: Linked Data). There are efforts around Swoogle to measure the size and characterize the content of the Semantic Web (Ding, Finin: Characterizing the Semantic Web on the Web). The Tabulator browser lets surfers browse interlinked data on the Semantic Web (Berners-Lee et al: Tabulator: Exploring and Analyzing linked data on the Semantic Web). Tools like D2R Server make it easy to publish existing data on on the Semantic Web (Bizer, Cyganiak: D2R Server – Publishing Relational Databases on the Semantic Web).

All these efforts are based on the assumption that, for being part of the Semantic Web, data should ideally fulfill the following requirements:

1. All entities of interest, such as information resources, real-world objects, and vocabulary terms should be identified by URI references.
2. URI references should be dereference-able, meaning that an application can look up a URI over the HTTP protocol and retrieve RDF data about the identified resource.
3. Data should be provided using the RDF/XML or Turtle syntax. If data is embedded inside other Web documents, for instance using Microformats inside an HTML page, then these documents should include hints how to automatically extract RDF data from them, for instance using GRDDL.
4. Data should be interlinked with other data. Thus resource descriptions should contain links to related information in the form of dereference-able URIs within RDF statements and rdfs:seeAlso links.

The Semantic Web Client Library regards all data that is published according to these rules as a single, global set of named RDF graphs."

Sunday, October 15, 2006

Interpreting Distributed Ontologies 

Interpreting Distributed Ontologies
Yuzhong Qu and Zhiqiang Gao
Semantic Web is challenged by the URI meaning issues arising from putting ontologies in open and distributed environments. As a try to clarify some of the meaning issues, this paper proposes a new approach to interpreting distributed ontologies, it’s built on the top of local models semantics, and extends it to deal with the URI sharing by harmonizing the local models via agreement on
vocabulary provenance. The commitment relationship is presented to allow the URI sharing between ontologies with richer semantics.

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