Internet Resources Discovery Metadata 3 1 H Weinberger
Internet Resources Discovery Metadata (3) 1 H. Weinberger - A. Frank
Contents of Metadata Lecture 1. Introduction to Metadata 2. Interoperability of Metadata 3. Evolution of Descriptive Metadata 4. Web Descriptive Metadata 5. Structured Metadata 6. Semantic Web 2 H. Weinberger - A. Frank
Content 1. Introduction 2. Context and Meaning 3. Web sites requirements: challenges and possible solutions 4. Web document standards l HTML and XML l Understanding RDF 3 H. Weinberger - A. Frank
2. Context & Meaning “Sometimes my whole world seems out of context” 5 H. Weinberger - A. Frank
3. Web Sites Requirements Standardize on logical views, not physical implementations. l Standard description of logical views available: l – l 6 More than databases actually did. Sites can interact with each other and with clients! H. Weinberger - A. Frank
3. 1 Challenges to Realize the Web’s Full Potential. . . l Find information intelligently. l Interact with applications on servers easily and efficiently. l But: physical implementations will vary from site to site. 7 H. Weinberger - A. Frank
3. 2 Information retrieval and descriptive metadata The need: exchange metadata from different schema. l The solution: l – – – 8 RDF: framework for syntax and structure XML: representation language DC: metadata schema H. Weinberger - A. Frank
4. Web Document Standards l l SGML HTML XML RDF - - Standard Generalized Markup Language - Hypertext Markup Language Extensible Markup Language Resource Description Framework SGML app HTML SGML 9 XML app RDF app. RDF- semantics XML- structure H. Weinberger - A. Frank
HTML l l 10 Began as a simple markup language for Web documents. Brought into closer compliance with SGML (HTML 2. 0 includes an SGML DTD). A DTD states what tags and attributes are used to describe content in an SGML document, where each tag is allowed, and which tags can appear within other tags. Common usage still flaunts SGML conventions. HTML l Structural elements: רשימה , טבלה , שורה חדשה , כותרות , פסקאות , גוף המסמך l Document appearance מירכוז וכיוצ"ב , גופן H. Weinberger - A. Frank – –
XML – What is it? Extensible Markup Language An XML document primarily consists of nested hierarchy of elements with a single root. Elements can contain character data, child elements, or a mixture of both – and they can have Attributes. l An XML markup language is defined in a DTD (Document Type Definition). l l l http: //www. cs. ucl. ac. uk/staff/A. Finkelstein/syllabusresources. html XML DTD declares: – – 11 Elements Attributes H. Weinberger - A. Frank
What is XML – what does it do l XML tags don’t describe user interface. There is no default presentation for each tag. They describe information. – – 12 XML has no special tags for titles or lists or paragraphs or images. It isn’t a presentation grammar. It is a way to encode any information. H. Weinberger - A. Frank
What is unique in XML vs. HTML l l Tags may not overlap each other. Example of illegal XML: – l Example of legal XML: – 13 <Person><Name>Adam</Name> <Key. Point><Heading>XML provides a data bus</Heading> </Person><More>…</More> </Key. Point> <Person> <Name>Adam Bosworth</Name> <Title>General Manager</Title> <Age>42</Age> </Person> H. Weinberger - A. Frank
XML's suitability as a universal data format for the Web Open standards and extensibility l Separation of content, presentation, linking l Computer platform and software application neutrality, interoperability l Unicode and data longevity l Will XML DTDs or schemas replace MARC? 14 H. Weinberger - A. Frank l
Root element XML examples Child ol ho c elements S L M X 15 H. Weinberger - A. Frank
XML- Towards Semantic Web XML: towards meta-grammer for interorganizational communication around the Web. l XML schema is an emerging standard from W 3 C. XML schema is a language for defining the structure of XML document instances that belong to a specific document type. l 16 H. Weinberger - A. Frank
XML DTDs Possibilities l l 17 Provide a formal and complete definition of an XML vocabulary. Are sharable descriptions of a the structure of an XML document. Are a way to validate specific instances of XML documents and constrain their content. Are restricted to on DTD per document instance. אפשר להגדיר מערכת של l מגדיר אלמנטים שסביר . שצריך בכל המסמכים הוא סוג HTML , לכאורה שמערב יסודות DTD של . מבניים עם צורניים l . DTD’s H. Weinberger - A. Frank l
RDF Objects : משפט בשפה טבעית l ( שייקספיר )ערך( הוא המחבר )סוג התייחסות( של )המחזה( המלט )משאב מתואר l l l 19 Resources: Things described (Hamlet) Properties: Specific aspects (attributes, relations) used to describe a resource (…Author) Statements: A specific resource + a named property + the value of that property for that resource (…Shakespeare) H. Weinberger - A. Frank
RDF Structural Model Resource Hamlet Property type creator Value Shakespeare A different metadata scheme might use author in place of creator, and , might use type for a different meaning, therefore, the RDF markup make explicit that this metadata is expressed in the DC schema, as follows: <DC: creator>Shakespeare</DC: creator> <DC: type>play</DC: type> A more precise Hamlet description, using imaginary URL: 20 <RDF: RDF> <RDF: description RDF: about=http: //hamlet. org/> <DC: creator>Shakespeare</DC: creator> <DC: type>play</DC: type> <RDF: description> <RDF: RDF> H. Weinberger - A. Frank
RDF Application Capabilities q q q 21 in resource discovery to provide better search engine capabilities. in cataloging for describing the content and content relationships. by intelligent software agents to facilitate knowledge sharing and exchange. in content rating in describing collections of pages that represent a single logical "document“. for describing Web pages. intellectual property rights of H. Weinberger - A. Frank
Web Metadata & Web Future l l 22 Searching on the web will become easier as search engines have more information available. Searching can be more focused. Doors will also be opened for automated software agents to roam the web. The web of today, the vast unstructured mass of information, may in the future be transformed into something more manageable - and thus something far more useful. H. Weinberger - A. Frank
References l l l 23 XML Adam Bosworth, XML: A Revolution Unfolds Cover, robin, Extensible Markup Language (XML) http: //www. oasis-open. org/cover/xml. html W 3 C Extensible Markup Language (XML) 1. 0 http: //www. xml. com/axml. html Ronald Bourret, Declaring Elements and Attributes in an XML DTD http: //www. rpbourret. com/xmldtd. htm XML DTD Example http: //www. cs. ucl. ac. uk/staff/A. Finkelstein/syllabusresources. ht ml RDF Site Summary (RSS) http: //groups. yahoo. com/group/rssdev/files/specification. html H. Weinberger - A. Frank
Contents of Metadata Lecture 1. Introduction to Metadata 2. Interoperability of Metadata 3. Evolution of Descriptive Metadata 4. Web Descriptive Metadata 5. Structured Metadata 6. Semantic Web 24 H. Weinberger - A. Frank
What is the Semantic Web? (1) l "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, Consistent logical web of data = Semantic Web 25 H. Weinberger - A. Frank
What is the Semantic Web? (2) l “The Web is about links; the Semantic Web is about the relationships implicit in those links. ” Dan Brickley l Semantic Web is part of the W 3 C technology and society domain. – l 26 Manage the development of enabling standards and technologies. The Semantic Web is a web whose content can be processed by computers. … an infrastructure for supplying the Web with formalized knowledge…” Jerome Euzenet, EU-NSF 2002 H. Weinberger - A. Frank
Research Organizations W 3 C l European Union Future Emergent Technology program (EU-FET) l National Science Foundation (NSF) l 27 H. Weinberger - A. Frank
Metadata & the Semantic Web l Meta-data is the fundamental building block of the Semantic Web. Mikael Nilsson et al. l Metadata architecture - envisioned as an "ecosystem" of ever-evolving interpretations layered upon objects as they are created, used and reused. Scott Wilson, CETIS staff (centre for educational technology interoperability standards) 28 H. Weinberger - A. Frank
The Current Web in Context l l l 29 Web is a set of Resources and Links Resources identified by URI's Uniform Resource Identifiers. To a user, this has become an exciting world To a machine, however, very little machinereadable information is avaliable. The meaning of the documents is clear to those with a grasp of (normally) English. The significance of the links is only evident from the context around the anchor. H. Weinberger - A. Frank
The Semantic Web - A Simple Extension to the Current Web 30 H. Weinberger - A. Frank (1)
The Semantic Web - A Simple Extension to the Current Web 31 H. Weinberger - A. Frank (2)
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