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Semantic Web

Semantic Web. Sushama Prasad CMSC 691C. Overview. Augment Web pages with data targeted at computers and add documents solely for computers, thus transform the Web into the Semantic Web.

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Semantic Web

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  1. Semantic Web Sushama Prasad CMSC 691C

  2. Overview • Augment Web pages with data targeted at computers and add documents solely for computers, thus transform the Web into the Semantic Web. • Computers will find the meaning of semantic data by following hyperlinks to definitions of key terms and rules for reasoning about them logically.

  3. Knowledge Representation • Computers must have access to structured collections of information and sets of inference rules that they can use to conduct automated reasoning. • Traditional KR systems typically require everyone to share exactly the same definition of common concepts such as "parent" or "vehicle” - narrow and idiosyncratic set of inferencing rules.

  4. The challenge? • Adding logic to the Web—the means to use rules to make inferences, choose courses of action and answer questions. • To provide a language that expresses both data and rules for reasoning about the data and that allows rules from any existing KR system to be exported onto the Web.

  5. Technologies • eXtensible Markup Language (XML) • allows users to add arbitrary structure to their documents but says nothing about what the structures mean. • Resource Description Framework (RDF) • expresses meaning, encodes it in sets of triples which can be written using XML tags. • a document makes assertions that particular things have properties with certain values. • subject, object and verb are each identified by a Universal Resource Identifier (URI).

  6. Ontologies – Collections of information • Two databases may use different identifiers for what is in fact the same concept, such as zip code. • The most typical kind of ontology for the Web has a taxonomy and a set of inference rules. • An ontology may express the rule "If a city code is associated with a state code, and an address uses that city code, then that address has the associated state code."

  7. Agents • Even agents that were not expressly designed to work together can transfer data among themselves when the data come with semantics. • Important facets of agents' functioning: • exchange of "proofs" written in the Semantic Web's unifying language • digital signatures • service discovery

  8. The next step… • The Semantic Web will break out of the virtual realm and extend into our physical world. • URIs can point to anything, including physical entities, which means we can use the RDF language to describe devices such as cell phones and TVs. • Work already done: • standard for describing functional capabilities of devices (such as screen sizes) and user preferences, called Composite Capability/Preference Profile (CC/PP).

  9. References • World Wide Web Consortium (W3C): www.w3.org/ • W3C Semantic Web Activity: www.w3.org/2001/sw/ • An introduction to ontologies: www.SemanticWeb.org/knowmarkup.html • DARPA Agent Markup Language (DAML) home page: www.daml.org/

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