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XML, RDF and Advanced Search (Semantic Web)

Thanks to Jim Hendler, Carl Lagoze, Jayavel Shanmugasundaram, Sara Cohen, Jonathan Mamou, Yaron Kanza, Mark Sapossnek, Yehoshua Sagiv, Frank van Harmelen. XML, RDF and Advanced Search (Semantic Web). What we have covered. What is IR Evaluation Tokenization and properties of text

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XML, RDF and Advanced Search (Semantic Web)

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  1. Thanks to Jim Hendler, Carl Lagoze, Jayavel Shanmugasundaram, Sara Cohen,Jonathan Mamou, Yaron Kanza, Mark Sapossnek, Yehoshua Sagiv, Frank van Harmelen XML, RDF and Advanced Search (Semantic Web)

  2. What we have covered • What is IR • Evaluation • Tokenization and properties of text • Web crawling • Query models • Vector methods • Measures of similarity • Indexing • Inverted files • Basics of internet and web • Spam and SEO • Search engine design • Google and Link Analysis • Social network analysis • This lecture: metadata, XML, RDF; issues in advanced search and the Semantic Web

  3. The importance of data and their rules • Tim Berners-Lee • inventor of the world wide web • Founder of the W3C • Presentation at Ted

  4. “Metadata is data about data” Metadata and Markup languages Metadata often is written in XML

  5. Metadata is semi-structured data conforming to commonlyagreed upon models, providing operational interoperabilityin a heterogeneous environment

  6. What is metadata?Some simple definitions • ‘Structured data about data’. • Dublin Core Metadata Initiative FAQ, 2005 • http://dublincore.org/resources/faq/ • Machine-understandable information about Web resources or other things. • Tim Berners-Lee, W3C, 1997 • http://www.w3.org/DesignIssues/Metadata

  7. "Web resources or other things" • Metadata might be "about"… anything! • HTML documents • digital images • databases • books • museum objects • archival records • metadata records • Web sites • collections • services • physical places • people • organizations • “works” • formats • concepts • events

  8. What is metadata?Towards a "functional" view • Data associated with objects which relieves their potential users of having to have full advance knowledge of their existence or characteristics. • Lorcan Dempsey & Rachel Heery, "Metadata: a current view of practice and issues",1998 • http://www.ukoln.ac.uk/metadata/publications/jdmetadata/ • Structured data about resources that can be used to help support a wide range of operations. • Michael Day, "Metadata in a Nutshell", 2001 • http://www.ukoln.ac.uk/metadata/publications/nutshell/

  9. What might metadata "say"? What is this called? What is this about? Who made this? When was this made? Where do I get (a copy of) this? When does this expire? What format does this use? Who is this intended for? What does this cost? Can I copy this? Can I modify this? What are the component parts of this? What else refers to this? What did "users" think of this? (etc!)

  10. What operations/functions? • resource disclosure & discovery • resource retrieval, use • resource management, including preservation • verification of authenticity • intellectual property rights management • commerce • content-rating • authentication and authorization • personalization and localization of services • (etc!)

  11. What operations/functions? • Different functions : different metadata • Metadata (and metadata standards) sometimes classified according to function • Descriptive: primarily for discovery, retrieval • Administrative: primarily for management • Structural: relationships between component parts of resources • Contextual: relationships between resources • No “one size fits all solution”!

  12. Metadata importance • “data about data” is about as good as the definition gets... • As a data resource grows, metadata becomes more important • Lack of metadata has different consequences • documentation: metadata can be regenerated automatically, or by hand • datasets, pictures: once lost, can be impossible to regenerate

  13. Types of Metadata • Descriptive • Discovery / description of objects • Title, author, abstract, etc. • Structural • Storage & presentation of objects • 1 pdf file, 1 ppt file, 1 LaTeX file, etc. • Administrative • Managing and preservation of objects • Access control lists, terms and conditions, format descriptions, “meta-metadata” See http://www.loc.gov/standards/metadata.html

  14. Which View is Correct? figure 1 from: http://www.dlib.org/dlib/january01/lagoze/01lagoze.html

  15. Approaches to Metadata • from Ng, Park and Burnett, 1997 (also JASIS, 50(13)) http://www.scils.rutgers.edu/~sypark/asis.html • library science: bibliographic control • “organizing the physical containers of information, by means of bibliographical description, subject analysis, and classification notation construction, so that the container can be efficiently described, identified, located and retrieved” • computer and information science: data management • “not only to store, access and utilize data effectively, but also to provide data security, data sharing, and data integrity”

  16. Metadata Formats and Implementation • Use markup languages • Interoperable • Extensible • Robust • Permits advance search features When online, the beginning of a semantic web!

  17. What is a markup language? • Textual (i.e. person readable) language where significant elements are indicated by markers • <TITLE>XML</TITLE> • Examples are RTF, HTML, XML, TEX etc. • Easy to process and can be manipulated by a variety of application programs

  18. Standard Generalized Markup Language (SGML) • Based on GML (generalized markup language), developed by IBM in the 1960s • An international standard (ISO 8879:1986) defines how descriptive markup should be embedded in a document • Can define any document format of any complexity • Enables, extensibility, structure and validation • Too many optional features for the Web • Gave birth to the extensible markup language (XML), W3C recommendation in 1998

  19. The Purpose of SGML • SGML is designed to make your information last longer than the systems that created it. Such longevity also implies immunity to short-term changes -- such as a change from one application program to another -- so SGML is also inherently designed for re-purposing and portability.

  20. What is SGML? • SGML (and it's derivatives, HTML and XML) are ASCII character based representations of electronic data • Remember, it's all bits--meaning is derived from how they are organized… • Think of SGML docs as strings that must be parsed--A web browser parses an HTML doc and uses the markup codes to display the data contained • Since it's all ASCII, these docs can also be handled by non parsing tools (such as vi, emacs, perl, etc.)

  21. SGMLXMLHTML • SGML is the “mother tongue” – but is overkill for most common desktop applications. • XML is an abbreviated version of SGML • easier to define own document types • easier for programmers to write programs to handle documents (and data) • omits all the options (and most of more complex and less-used parts) of SGML) • HTML is just one of many SGML or XML “applications” – most frequently used on the Web

  22. SGML Components • SGML documents have three parts: • Declaration: specifies which characters and delimiters may appear in the application • DTD (document type definition) / style sheet: defines the syntax of markup constructs • Document instance: actual text (with the tag) of the documents • More info could be found: http://www.W3.Org/markup/SGML

  23. World Wide Web (W3C) Consortium

  24. What is XML? • XML – eXtensible Markup Language • designed to improve the functionality of the Web by providing more flexible and adaptable information and identification • “extensible” because not a fixed format like HTML • a language for describing other languages (a meta-language) • design your own customised markup language

  25. The HTML World <body> <h1> XML and Information Retrieval: A SIGIR 2000 Workshop </h1> <p> The workshop was held on 28 July 2000. The editors of the workshop were David Carmel, Yoelle Maarek, and Aya Soffer </p> <h2> XQL and Proximal Nodes </h2> <p> The paper was authored by Ricardo Baeza-Yates and Gonzalo Navarro. The abstract of this paper is given below. </p> <p> We consider the recently proposed language … </p> <p> The paper references the following papers: <a href=“http://www.acm.org/www8/paper/xmlql”> … </a> … </p> …

  26. The XML World <workshopdate=”28 July 2000”> <title> XML and Information Retrieval: A SIGIR 2000 Workshop </title> <editors> David Carmel, Yoelle Maarek, Aya Soffer </editors> <proceedings> <paperid=”1”> <title> XQL and Proximal Nodes </title> <author> Ricardo Baeza-Yates </author> <author> Gonzalo Navarro </author> <abstract> We consider the recently proposed language … </abstract> <sectionname=”Introduction”> Searching on structured text is becoming more important with XML … <subsection name=“Related Work”> The XQL language … </subsection> </section> … <citexmlns:xlink=”http://www.acm.org/www8/paper/xmlql> … </cite> </paper> …

  27. Why use XML? • XML is written in SGML – the Standardized General Markup Language, an international standard (ISO 8879) • XML = very simple dialect of SGML • goal = enable generic SGML to be served, received and processed on the Web in ways not possible with HTML

  28. Why use XML? • XML is not just for Web pages • use to store any kind of structured document • to enclose/encapsulate information in order to pass it between different computing systems that are otherwise unable to communicate

  29. Key feature of XML • An application is free to use XML tagged data in many different ways, e.g. • produce an image • generate a formatted text listing • display the XML document’s markup in pretty colors • restructure the data into a format for storing in a database, transmission over a network, input to another program.

  30. XML is important because... • Removes 2 constraints that held back Web development: • dependence on a single, inflexible document type (HTML) [much abused] • reduced the complexity of full SGML [many options but hard to program]

  31. XML… allows the flexible development of user-defined document types. • provides a robust, non-proprietary, persistent, and verifiable file format for the storage and transmission of text and data both on and off the Web

  32. XML Software? • many programs are “XML ready” already today. • xml.coverpages.org covers news of new additions to XML

  33. Is XML a Computer Language? • XML is not C or C++ or like any other programming language • By itself, it cannot specify calculations, actions, decisions to be carried out in any order • XML is a markup specification language

  34. XML - a Markup Language • with XML, you can design ways of describing information (text or data), usually for storage, transmission or processing by a program • XML conveys no information about what should be done with the data or text – it merely describes it. • By itself, XML does anything – it is a data description format

  35. How do I run or execute an XML file? • You can’t and you don’t ! • XML is not a programming language • XML is a markup specification language • XML files are just data (waiting for a program to do something with them) • XML files can be viewed with an XML editor or XML-compatible browser

  36. Things to Remember • XML does not replace HTML – it provides an alternative which allows you to define your own set of markup elements to a published standard: • <?xml version="1.0" standalone="yes"?> • <conversation> • <greeting>Hello, world!</greeting> • <response>Stop the planet, I want to get off!</response> • </conversation>

  37. Things to Remember • All parts of an XML document are case sEnSiTiVe • Element type names are case sensitive, so <BODY> …</b ody> is out. • Attribute names are case sensitive … • <PIC width=“7cm”/> and • <PIC WIDTH=“6cm”/> • describe different attributes, not just different values for the attribute “PIC width”.

  38. What is XQuery? • XQuery is the language for querying XML data • The best way to explain XQuery is to say that XQuery is to XML what SQL is to database tables. • XQuery uses XPath expressions to extract XML data. • XPath is a language for finding information in an XML document. • XPath is used to navigate through elements and attributes in an XML document. • XQuery is defined by the W3C. • XQuery is supported by all the major database engines (IBM, Oracle, Microsoft, etc.) • XQuery 1.0 W3C Recommendation

  39. Motivation for XML Search • It is becoming increasingly popular to publish data on the Web in the form of XML documents. • Current search engines, which are an indispensable tool for finding HTML documents, have two main drawbacks when it comes to searching for XML documents. • It is not possible to pose queries that explicitly refer to XML tags. • Search engines return references (i.e. links) to documents and not specific fragments thereof. This is problematic, since large XML documents may contain thousands of elements storing many pieces of information that are not necessarily related to each other.

  40. The HTML World <body> <h1> XML and Information Retrieval: A SIGIR 2000 Workshop </h1> <p> The workshop was held on 28 July 2000. The editors of the workshop were David Carmel, Yoelle Maarek, and Aya Soffer </p> <h2> XQL and Proximal Nodes </h2> <p> The paper was authored by Ricardo Baeza-Yates and Gonzalo Navarro. The abstract of this paper is given below. </p> <p> We consider the recently proposed language … </p> <p> The paper references the following papers: <a href=“http://www.acm.org/www8/paper/xmlql”> … </a> … </p> …

  41. The XML World <workshopdate=”28 July 2000”> <title> XML and Information Retrieval: A SIGIR 2000 Workshop </title> <editors> David Carmel, Yoelle Maarek, Aya Soffer </editors> <proceedings> <paperid=”1”> <title> XQL and Proximal Nodes </title> <author> Ricardo Baeza-Yates </author> <author> Gonzalo Navarro </author> <abstract> We consider the recently proposed language … </abstract> <sectionname=”Introduction”> Searching on structured text is becoming more important with XML … <subsection name=“Related Work”> The XQL language … </subsection> </section> … <citexmlns:xlink=”http://www.acm.org/www8/paper/xmlql> … </cite> </paper> …

  42. Problems with XQuery • A query language for XML, such as XQuery, can be used to extract data from XML documents. • However, such a query language is not an alternative to an XML search engine for several reasons. • The syntax of XQuery is more complicated than the syntax of a standart search query. Hence, it is not appropriate for a naive user. • Extensive knowledge of the document structure is required in order to correctly formulate a query. Thus, queries must be formulated on a per document basis. • XQuery lacks any mechanism for ranking answers. • Solution - XML Search engine

  43. XML Search Tool Design Features? • A simple syntax that can be used by naive users • Search results should include XML fragments and not necessarily full documents • The XML fragments in an answer, should be semantically related • For example, a paper and an author should be in an answer only if the paper was written by this author • Search results should be ranked • Search results should be returned in “reasonable” time

  44. XML Search Engines • Summary of XML engines • Open source ones starting to emerge • Or just use web search engine with filetype:xml • Usually doesn’t work! • Many for commercial use and some in design • Active research area • Web XML is a step in the direction of the semantic web!

  45. What is Web 2.0 ? • Term coined by Tim O’Reilly and Media Live International as part of brainstorming session about the future of the web in 2005 • Also may be called the Live Web or Living Web • Refers to more interactive technologies that engage, facilitate and empower users • Companies utilizing interactive technologies are the hot investments • Companies are just starting to embrace these technologies for business value • Tim’s Def (Video); Schmidt’s (Video) • The Machine (Video)

  46. Web 1.0 vs 2.0 (Some Examples) Source: www.oreilly.com, “What is web 2.0: Design Patterns and Business Models for the next Generation of Software”, 9/30/2005

  47. Web 3.0This will be the INTELLIGENT Web! The Semantic Web!

  48. Now... that should clear up a few things around here How will we get the semantic web?

  49. The Web and Web 2.0 were designed with humans in mind. (Human Understanding) • The Web 3.0 will anticipate our needs! Whether it is State Department information when traveling, foreign embassy contacts, airline schedules, hotel reservations, area taxis, or famous restaurants: the information. The new Web will be designed for computers. (Machine Understanding) • The Web 3.0 will be designed to anticipate the meaning of the search.

  50. Web 2.0 vs Web 3.0 Web 2.0 : On the Web, you can see your e-mails, photographs, and restaurant appointments. Web 3.0: On the Web... ...you can see your photographs arranged so that you know what restaurants you visited on a particular date, and based on related emails sent that day.

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