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Internet Resources Discovery

This lecture covers the evolution of descriptive metadata, the interoperability of metadata, and the use of structured and semantic web descriptive metadata in web resources. It also discusses the challenges and possible solutions in implementing metadata standards.

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Internet Resources Discovery

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  1. Internet Resources Discovery Metadata (3) H. Weinberger - A. Frank

  2. 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 H. Weinberger - A. Frank

  3. Content • Introduction • Context and Meaning • Web sites requirements: challenges and possible solutions • Web document standards • HTML and XML • Understanding XML • Understanding RDF H. Weinberger - A. Frank

  4. 1. Introduction • מידע-על מבני Structured metadata הוא מידע-על מובנה (פורמלי) מובן למכונה (מחשב) • מונחים נרדפים בשימוש: שפות סימון, שפות תחביר • שפות סימון מתארות מבנה (Structure) ופורמט Format)) בהם מוצג הטקסט. • מידע-על מבני בדרך כלל נפרד מהתכנים. • שיטות ההבניה הנפוצות ביותר בשימוש הן ממשפחת SGML שהיא: • מערכת כללים לתיאור תחביר (Markup specification). • מפרט מסוים שמוגדר באמצעות SGMLDocument Type Definition .(DTD) H. Weinberger - A. Frank

  5. 2. Context & Meaning “Sometimes my whole world seems out of context” H. Weinberger - A. Frank

  6. 3. Web Sites Requirements • Standardize on logical views, not physical implementations. • Standard description of logical views available: • More than databases actually did. • Sites can interact with each other and with clients! H. Weinberger - A. Frank

  7. 3.1 Challenges to Realize the Web’s Full Potential... • Find information intelligently. • Interact with applications on servers easily and efficiently. • But: physical implementations will vary from site to site. H. Weinberger - A. Frank

  8. 3.2 Information retrieval and descriptive metadata • The need: exchange metadata from different schema. • The solution: • RDF: framework for syntax and structure • XML: representation language • DC: metadata schema H. Weinberger - A. Frank

  9. 4.Web Document Standards • SGML - Standard Generalized Markup Language • HTML - Hypertext Markup Language • XML - Extensible Markup Language • RDF - Resource Description Framework HTML SGML app XML app RDF app. RDF- semantics SGML XML- structure H. Weinberger - A. Frank

  10. HTML • 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 • Structural elements: • גוף המסמך, פסקאות, כותרות, שורה חדשה, טבלה, רשימה • Document appearance • גופן, מירכוז וכיוצ"ב H. Weinberger - A. Frank

  11. 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. • An XML markup language is defined in a DTD (Document Type Definition). • http://www.cs.ucl.ac.uk/staff/A.Finkelstein/syllabusresources.html • XML DTD declares: • Elements • Attributes H. Weinberger - A. Frank

  12. XML tags don’t describe user interface. There is no default presentation for each tag. They describe information. 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. What is XML – what does it do H. Weinberger - A. Frank

  13. What is unique in XML vs. HTML • Tags may not overlap each other. • Example of illegal XML: • <Person><Name>Adam</Name><KeyPoint><Heading>XML provides a data bus</Heading> </Person><More>…</More> </KeyPoint> • Example of legal XML: • <Person><Name>Adam Bosworth</Name> <Title>General Manager</Title> <Age>42</Age></Person> H. Weinberger - A. Frank

  14. XML's suitability as a universal data format for the Web • Open standards and extensibility • Separation of content, presentation, linking • Computer platform and software application neutrality, interoperability • Unicode and data longevity • Will XML DTDs or schemas replace MARC? H. Weinberger - A. Frank

  15. Root element XML examples Child elements XML School H. Weinberger - A. Frank

  16. XML- Towards Semantic Web • XML: towards meta-grammer for inter-organizational communication around the Web. • XML schema is an emerging standard from W3C. XML schema is a language for defining the structure of XML document instances that belong to a specific document type. H. Weinberger - A. Frank

  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 .DTD’s מגדיר אלמנטים שסביר שצריך בכל המסמכים. לכאורה, HTML הוא סוג של DTD שמערב יסודות מבניים עם צורניים. XML DTDs Possibilities H. Weinberger - A. Frank

  18. Resource Description Framework (RDF) • שיטה באמצעותה ניתן לבצע חילופין של מידע-על: • כן: מודל מבני לביטוי תחביר. • לא: ציון סמנטיקה של מידע-על. • בסכמת מידע-על, דוגמת DC, קיימים שלושה היבטים: • Semantic: ההיבט הסמנטי מתאר כיצד להבין מושגים כמו Data, Creatorכיצד להבין מושגים כמו creator, לדוגמא, לציין שהכוונה במובן DC • Syntax: ההיבט התחבירי מפרט כיצד לבטא את המידע-על לדוגמא: תאור המחבר ייעשה באמצעות האלמנט creator. • Structure : מבנה מגדיר יחסים בין אלמנטים של מידע-על לדוגמא: יום, תאריך ושנה H. Weinberger - A. Frank

  19. RDF Objects • משפט בשפה טבעית: שייקספיר (ערך) הוא המחבר (סוג התייחסות) של (המחזה) המלט (משאב מתואר) • 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

  20. RDF Structural Model • Resource Property type ValueHamletcreatorShakespeare 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: <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

  21. RDF Application Capabilities • 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 intellectual property rights of Web pages. H. Weinberger - A. Frank

  22. Web Metadata & Web Future • 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

  23. References • XML Adam Bosworth, XML:A Revolution Unfolds • Cover, robin, Extensible Markup Language (XML) http://www.oasis-open.org/cover/xml.html • W3C Extensible Markup Language (XML) 1.0 http://www.xml.com/axml/axml.html • Ronald Bourret, Declaring Elements and Attributes in an XML DTD http://www.rpbourret.com/xml/xmldtd.htm • XML DTD Example http://www.cs.ucl.ac.uk/staff/A.Finkelstein/syllabusresources.html • RDF Site Summary (RSS) http://groups.yahoo.com/group/rss-dev/files/specification.html H. Weinberger - A. Frank

  24. 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 H. Weinberger - A. Frank

  25. What is the Semantic Web? (1) • "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 H. Weinberger - A. Frank

  26. What is the Semantic Web? (2) • “The Web is about links; the Semantic Web is about the relationships implicit in those links.” Dan Brickley • Semantic Web is part of the W3C technology and society domain. • 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

  27. Research Organizations • W3C • European Union Future Emergent Technology program (EU-FET) • National Science Foundation (NSF) H. Weinberger - A. Frank

  28. Metadata & the Semantic Web • Meta-data is the fundamental building block of the Semantic Web. Mikael Nilsson et al. • 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) H. Weinberger - A. Frank

  29. The Current Web in Context • 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 machine-readable information is avaliable. • The meaning of the documents is clear tothose with a grasp of (normally) English.The significance of thelinks is only evident from the context around the anchor. H. Weinberger - A. Frank

  30. The Semantic Web - A Simple Extension to (1)the Current Web H. Weinberger - A. Frank

  31. The Semantic Web - A Simple Extension to (2)the Current Web H. Weinberger - A. Frank

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