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Semantic Web - Overview Semantic Web - Overview Presentation Transcript

  • Faculty of Science, Technology and Communication (FSTC) Bachelor en Informatique (professionnel) Semantic Web Unit 2: Semantic Web – Overview Rules Data Trust Data Proof Ontology vocabula ry RDF + RD F Schem a Digital Signature Logic XML + N amespac es + XML Schema •URI •Unicode Semantic Web ::: Serge Linckels, 2013 ::: www.linckels.lu ::: serge@linckels.lu ::: 1
  • 2. Semantic Web – Overview 2.1. About the "Classical" Web 2.2. Introduction to Semantics 2.3. Vision of the Semantic Web 2.4. Closer Look at HTML 2.5. Lessons Learned 2.6. Semantic Web Architecture 2.7. Applications of the Semantic Web 2.8. Conclusion 2.9. References Semantic Web ::: Serge Linckels, 2013 ::: www.linckels.lu ::: serge@linckels.lu ::: 2
  • 2. Semantic Web – Overview 2.1. About the "Classical" Web em S an s? tic Ho w se to e m an xpr tic ess s er? alkill Seri em S nt a s? ic Semantic Web ::: Serge Linckels, 2013 ::: www.linckels.lu ::: serge@linckels.lu ::: 3 View slide
  • 2. Semantic Web – Overview 2.1. About the "Classical" Web "Web 2.0 is the business revolution in the computer industry caused by the move to the Internet as platform, and an attempt to understand the rules for success on that new platform." (Tim O'Reilly, 2003) The Web 2.0 is a serviceoriented environment that gives the users the freedom and technological means to actively contribute to Web content The term "Web 2.0" describes the changing trends in the use of World Wide Web technology and web design that aim to enhance creativity, communications, secure information sharing, collaboration and functionality of the web. Web 2.0 concepts have led to the development and evolution of web-culture communities and hosted services, such as social-networking sites, video sharing sites, wikis, blogs, and folksonomies. Although the term suggests a new version of the World Wide Web, it does not refer to an update to any technical specifications, but rather to changes in the ways software developers and end-users utilize the Web. "Social Web" Semantic Web ::: Serge Linckels, 2013 ::: www.linckels.lu ::: serge@linckels.lu ::: 4 View slide
  • 2. Semantic Web – Overview 2.1. About the "Classical" Web Folksonomy: different people have different perceptions of the same object. Such perceptions can be grouped to classify and identify users. Everyone can tag objects in the Web (social tagging). The set of tags gives a tag cloud. Popular folksonomies : Semantic Web ::: Serge Linckels, 2013 ::: www.linckels.lu ::: serge@linckels.lu ::: 5
  • 2. Semantic Web – Overview 2.1. About the "Classical" Web Semantic Web Web is a service on the Internet The Web is also a place where: - computers do the presentation (easy) - people do the linking and interpreting (hard) Why not get computers to do more of the hard work? Semantic Web ::: Serge Linckels, 2013 ::: www.linckels.lu ::: serge@linckels.lu ::: 6
  • 2. Semantic Web – Overview 2.2. Introduction to Semantics Semantic Web "Classical Web" Syntax is the study of the structure of sign systems, focusing on the form, not the meaning Semantic Web Semantics refers to aspects of meaning, as expressed in language or other systems of signs Pragmatics is the study of the practical use of signs by agents or communities of interpretation within particular circumstances and contexts I movies the go to with my wife I go to the movies with my wife The movies went to me Is the window open? [The asking person may feel cold] Semantic Web ::: Serge Linckels, 2013 ::: www.linckels.lu ::: serge@linckels.lu ::: 7
  • 2. Semantic Web – Overview 2.3. Vision of the Semantic Web Semantic Web = a vision of Tim Berners-Lee http://www.whatissemanticweb.com/2013/05/top-must-watch-ted-videosrelated-to.html “... a goal of the Web was that, if the interaction between person and hypertext could be so intuitive that the machine-readable information space gave an accurate representation of the state of people's thoughts, interactions, and work patterns, then machine analysis could become a very powerful management tool, seeing patterns in our work and facilitating our working together through the typical problems which beset the management of large organizations.” (Scientific American, May, 2001) Classical Web is build upon HTML (HyperText Markup Language). Can HTML be used to build the Semantic Web? Semantic Web ::: Serge Linckels, 2013 ::: www.linckels.lu ::: serge@linckels.lu ::: 8
  • 2. Semantic Web – Overview 2.4. Closer Look at HTML A markup language provides a way to combine a text and extra information about it, like structure and layout. Christoph Meinel Viola Brehmer Long Wang Feng Cheng Dirk Cordel Serge Linckels Harald Sack <h1>Christoph Meinel</h1> <h2>Viola Brehmer</h2> <ul> <li>Long Wang</li> <li>Feng Cheng</li> <li>Dirk Cordel</li> <li>Serge Linckels</li> </ul> Harald Sack HTML adds structure and layout to the content. But neither a machine, nor a human can understand the sense of the content.   Semantic Web ::: Serge Linckels, 2013 ::: www.linckels.lu ::: serge@linckels.lu ::: 9
  • 2. Semantic Web – Overview 2.4. Closer Look at HTML Limitations and problems of HTML: Everyone builds Web pages, without rules and discipline. Attempt for remediation: W3C compatibility initiative HTML lacks of standardization (incompatibilities between browsers) HTML lacks of expressivity No semantics can be expressed Poor possibilities for querying the Web (mostly by keywords over the content) others… Semantic Web ::: Serge Linckels, 2013 ::: www.linckels.lu ::: serge@linckels.lu ::: 10
  • 2. Semantic Web – Overview 2.5. Lessons Learned Classical Web Semantic Web Based on HTML which is not sufficient to express semantics Requires new languages and technologies to express semantics No reasoning (logical inference) is possible over the data Reasoning over data is possible, e.g., better search results Uncontrolled growth: lots of extensions causing incompatibilities Controlled growth according a roadmap How it began 1997, WWW7 in Brisbane, Australia: Tim Berners-Lee presents his Vision about a "Global Reasoning Web" 1998, WWW8 in Toronto, Canada: Tim Berners-Lee presents the "Semantic Web Roadmap" 2001, Scientific America publishes an article about the vision of the Semantic Web; the article becomes the most cited reference to the Semantic Web Semantic Web ::: Serge Linckels, 2013 ::: www.linckels.lu ::: serge@linckels.lu ::: 11
  • 2. Semantic Web – Overview 2.6. Semantic Web Architecture Semantic Web Roadmap: Controlled growth bottom up according to this architecture. Architecture was (slightly) modified in the last years. Semantic Web ::: Serge Linckels, 2013 ::: www.linckels.lu ::: serge@linckels.lu ::: 12
  • 2. Semantic Web – Overview 2.6. Semantic Web Architecture Resource = {(data,metadata), rules} Data: can be anything Metadata: textual annotation (Unicode) Each resource has a Unified Resource Identifier (URI) in Unicode Internationalized Resource Identifier (IRI) is a generalization / complement of URI Classical Web Semantic Web Composed of Web pages Composed of resources Each Web page has a URL Each resource has a URI Web pages have multimedia content A resource can be anything No semantic description of the content Metadata describe semantics of the content Web pages are independent sets of information Resources depend on applications; they are processed in a given context Semantic Web ::: Serge Linckels, 2013 ::: www.linckels.lu ::: serge@linckels.lu ::: 13
  • 2. Semantic Web – Overview 2.6. Semantic Web Architecture XML: shared vocabulary Gives structure to metadata using a specific set of elements (tags) in a shared domain Description of how data are to be used (first step to describe semantics) Independent and standardized file exchange format Christoph Meinel Viola Brehmer Long Wang Feng Cheng Dirk Cordel Serge Linckels Harald Sack <ChairMeinel> <Professor> <FirstName>Christoph</FirstName> <LastName>Meinel</LastName> </Professor> <Secretary>Viola Brehmer</Secretary> <PhDStudent>Long Wang</PhDStudent> <PhDStudent>Feng Cheng</PhDStudent> <PhDStudent>Dirk Cordel</PhDStudent> <PhDStudent>Serge Linckels</PhDStudent> <FormerPhDStudent>Harald Sack</FormerPhDStudent> </ChairMeinel> Semantic Web ::: Serge Linckels, 2013 ::: www.linckels.lu ::: serge@linckels.lu ::: 14
  • 2. Semantic Web – Overview 2.6. Semantic Web Architecture RDF: abstract syntax with formal semantics Graphical formalism to describe semantic relations between resources Sharing of taxonomies and vocabularies Different serialization formats, e.g., XML Different query languages, e.g., SPARQL full name Christoph Meinel title Prof. Dr Christoph Meinel http://www.hpi.uni-potsdam.de/meinel.html Resource role Scientific Director of HPI role Board Member Semantic Web ::: Serge Linckels, 2013 ::: www.linckels.lu ::: serge@linckels.lu ::: 15
  • 2. Semantic Web – Overview 2.6. Semantic Web Architecture OWL: ontologies and reasoning Powerful formalism to represent classes of objects and their properties in form of ontologies Sharing of ontologies Logical inferences over data Defining rules over data Powerful reasoning framework, i.e., Description Logics Set of resources: Professor{Christoph Meinel} PhDstudent{Ji, Long, Dirk, Serge} Properties: isProfessorOf(Christoph Meinel,Dirk) isProfessorOf(Christoph Meinel,Ji) By logical induction: DoctorFather  Professor  isProfessorOf.PhDstudent Semantic Web ::: Serge Linckels, 2013 ::: www.linckels.lu ::: serge@linckels.lu ::: 16
  • 2. Semantic Web – Overview 2.6. Semantic Web Architecture Logic, Proof, Trust Are the semantic data reliable and trustful? Have the data been manipulated? Public key encryption Digital signatures Semantic document = resource + set of assertions n ryptio nc ML E X XML S ecurity URIs XM L Si gn at u Semantic Web ::: Serge Linckels, 2013 ::: www.linckels.lu ::: serge@linckels.lu ::: re 17
  • 2. Semantic Web – Overview 2.7. Applications of the Semantic Web Web based applications Help the user find what (s)he is looking for by a better understanding of the sense of the query. Example: "Hotel in Wien with a large bed and a TV set" Agents (robots) can better index resources on the Web. Personalization of search engines. Example: The user lives in Wien and prefers a large TV set Make explicit some implicit knowledge. Example: Where can I get gasoline? Answer can be the result of a logicial inference. Not Web base applications Different domains need (and use already) systems that implement Semantic Web technologies. Examples: - medicine, pharma industry - e-Learning - travel agencies - digital libraries -… Semantic Web ::: Serge Linckels, 2013 ::: www.linckels.lu ::: serge@linckels.lu ::: 18
  • 2. Semantic Web – Overview 2.8. Conclusion The Semantic Web is… A vision of a new Web that shall replace the "classical Web" Several technologies were (or are about to be) created to build the Semantic Web The Semantic Web does not exists yet, but different kind of applications do already implement related technologies The Semantic Web is (still) a hot topic in ongoing research The Semantic Web is not… Some kind of artificial intelligence that makes stupid search engines yield better results Semantic Web ::: Serge Linckels, 2013 ::: www.linckels.lu ::: serge@linckels.lu ::: 19
  • 2. Semantic Web – Overview 2.9. References E-Librarian Service User-Friendly Semantic Search in Digital Libraries Serge Linckels, Christoph Meinel Creating the Semantic Web with RDF: Professional Developer's Guide Johan Hjelm Foundations of Semantic Web Technologies Pascal Hitzler, Markus Krötzsch, Sebastian Rudolph Semantic Web ::: Serge Linckels, 2013 ::: www.linckels.lu ::: serge@linckels.lu ::: 20