Semantic Web. Semantic Web: Resource Description Framework (RDF) cont. Resource Description Framework (RDF) W3C Definition:

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1 Semantic Web: The Semantic Web is an extension of the current web in which information is given well-defined meaning, better enabling computers and people to work in cooperation. Tim Berners-Lee, James Hendler, Ora Lassila, The Semantic Web, Scientific American, May 2001 W3C Definition: Semantic Web The Semantic Web is the representation of data on the World Wide Web. It is a collaborative effort led by W3C with participation from a large number of researchers and industrial partners. It is based on the Resource Description Framework (RDF), which integrates a variety of applications using XML for syntax and URIs for naming. WS 2004/2005, Dokumentverarbeitung, Prof. Dr. D. Rösner; Version: 27. Januar WS 2004/2005, Dokumentverarbeitung, Prof. Dr. D. Rösner; Version: 27. Januar Resource Description Framework (RDF) an XML text format that supports resource description and metadata applications... For example, RDF might let you identify people in a Web photo album using information from a personal contact list; then your mail client could automatically start a message to those people stating that their photos are on the Web.... RDF provides tools to integrate even more, to make the Web a little bit more into a Semantic Web. from: XML in 10 points (cf. Resource Description Framework (RDF) cont. Just like people need to have agreement on the meanings of the words they employ in their communication, computers need mechanisms for agreeing on the meanings of terms in order to communicate effectively. Formal descriptions of terms in a certain area (shopping or manufacturing, for example) are called ontologies and are a necessary part of the Semantic Web. RDF, ontologies, and the representation of meaning so that computers can help people do work are all topics of the Semantic Web Activity. from: XML in 10 points (cf. WS 2004/2005, Dokumentverarbeitung, Prof. Dr. D. Rösner; Version: 27. Januar WS 2004/2005, Dokumentverarbeitung, Prof. Dr. D. Rösner; Version: 27. Januar

2 Dublin Core Metadata Initiative The Dublin Core Metadata Initiative is an open forum engaged in the development of interoperable online metadata standards that support a broad range of purposes and business models. DCMI s activities include consensus-driven working groups, global workshops, conferences, standards liaison, and educational efforts to promote widespread acceptance of metadata standards and practices. Die definierten Elemente: Title Format Creator Identifier Subject Source Description Language Publisher Relation Contributor Coverage Date Rights Type Dublin Core Metadata Initiative WS 2004/2005, Dokumentverarbeitung, Prof. Dr. D. Rösner; Version: 27. Januar WS 2004/2005, Dokumentverarbeitung, Prof. Dr. D. Rösner; Version: 27. Januar Element Name: Title Label: Title Beispiele für Definitionen von Elementen: Definition: A name given to the resource. Comment: Typically, Title will be a name by which the resource is formally known. Beispiele für Definitionen von Elementen: cont. Element Name: Creator Label: Creator Definition: An entity primarily responsible for making the content of the resource. Comment: Examples of Creator include a person, an organization, or a service. Typically, the name of a Creator should be used to indicate the entity. WS 2004/2005, Dokumentverarbeitung, Prof. Dr. D. Rösner; Version: 27. Januar WS 2004/2005, Dokumentverarbeitung, Prof. Dr. D. Rösner; Version: 27. Januar

3 Beispiele für Definitionen von Elementen: cont. Element Name: Description Label: Description Definition: An account of the content of the resource. Comment: Examples of Description include, but is not limited to: an abstract, table of contents, reference to a graphical representation of content or a free-text account of the content. Beispiele für Definitionen von Elementen: cont. Element Name: Format Label: Format Definition: The physical or digital manifestation of the resource. Comment: Typically, Format may include the media-type or dimensions of the resource. Format may be used to identify the software, hardware, or other equipment needed to display or operate the resource. Examples of dimensions include size and duration. Recommended best practice is to select a value from a controlled vocabulary (for example, the list of Internet Media Types [MIME] defining computer media formats). WS 2004/2005, Dokumentverarbeitung, Prof. Dr. D. Rösner; Version: 27. Januar WS 2004/2005, Dokumentverarbeitung, Prof. Dr. D. Rösner; Version: 27. Januar Nachfolger von PICS: Platform for Internet Content Selection RDF ist deklarativ mit XML werden Metadaten repräsentiert in Form von Aussagen über Eigenschaften und Beziehungen sog. Resourcen Resource kann alles sein, was eine URL besitzt nutzt Arbeiten zur Wissensrepäsentation (z.b. semantische Netze) Tripel in Analogie zu Subjekt, Verb und Objekt elementarer Sätze Beispiel: (field 5 in database A) (is a field of type) (zip code) URIs zur Identifikation der Elemente im Tripel cf. Tim Berners-Lee, James Hendler, Ora Lassila, The Semantic Web, Scientific American, May 2001 WS 2004/2005, Dokumentverarbeitung, Prof. Dr. D. Rösner; Version: 27. Januar WS 2004/2005, Dokumentverarbeitung, Prof. Dr. D. Rösner; Version: 27. Januar

4 ein einfaches Beispiel: <RDF xmlns=" xmlns:dc=" <Description about=" <dc:title>the W3C Folio 1999</dc:title> <dc:creator>w3c Communications Team</dc:creator> <dc:date> </dc:date> <dc:subject>web development, World Wide Web Consortium, Interoperability of the Web</dc:subject> </Description> </RDF> Erläuterungen zum Beispiel: Zeile 1: eine RDF Description Zeile 2: als Vokabular wird Dublin Core verwendet Zeile 3: um welche Resource handelt es sich? cf. WS 2004/2005, Dokumentverarbeitung, Prof. Dr. D. Rösner; Version: 27. Januar WS 2004/2005, Dokumentverarbeitung, Prof. Dr. D. Rösner; Version: 27. Januar Erläuterungen zum Beispiel: Zeile 4 bis 7: die eigentlichen Metadaten als RDF-Aussagen (RDF statements) über die DC-Elemente title creator date subject XML-Namespaces können bei Namenskonflikten in RDF-Vokabularen genutzt werden Beispiel: address könnte in einem Vokabular die Bedeutung Ort einer Firma haben, in einem anderen aber für ihre Adresse im Web stehen cf. WS 2004/2005, Dokumentverarbeitung, Prof. Dr. D. Rösner; Version: 27. Januar WS 2004/2005, Dokumentverarbeitung, Prof. Dr. D. Rösner; Version: 27. Januar

5 Ontology?... traditionally defined as the science or study of being (Oxford English Dictionary) In AI, usually attributed to (Gruber, 1993) the notion of ontology is, essentially, the specification of a conceptualization Ontology as specification of a conceptualization... as specification of a conceptualization : that is, defined terms and relationships between them, usually in some formal (preferably machine-readable) manner. as it is currently being used in semantic web circles that, is, as a set of knowledge terms, including the vocabulary, the semantic interconnections and some simple rules of inference and logic, for some particular topic. cf. hendler/agentweb.html WS 2004/2005, Dokumentverarbeitung, Prof. Dr. D. Rösner; Version: 27. Januar WS 2004/2005, Dokumentverarbeitung, Prof. Dr. D. Rösner; Version: 27. Januar Ontology? From cf. hendler/agentweb.html:... For example the ontology of cooking and cookbooks includes ingredients, how to stir and combine them, the difference between simmering and deep-frying, Ontology? ontology of cooking and cookbooks... the expectation that the products will be eaten or drunk, that oil is for cooking in or consuming and not for lubrication, and so forth. WS 2004/2005, Dokumentverarbeitung, Prof. Dr. D. Rösner; Version: 27. Januar WS 2004/2005, Dokumentverarbeitung, Prof. Dr. D. Rösner; Version: 27. Januar