Current State of the Semantic Web

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1 Current State of the Semantic Web Kore Nordmann March 6, 2009

2 About me Kore Nordmann, Long time PHP developer Regular speaker, author, etc. Studies computer science in Dortmund Consultancy and software development Active open source developer: ez Components (Graph, WebDav, Document), Arbit, PHPUnit, Torii, PHPillow, KaForkL, Image 3D, WCV,...

3 Outline The term History Expressing semantics Outlook

4 The term Semantics Association of meaning to structures Orginates from: σηµαντ ικoς (semantikos), significant

5 The term Semantics Association of meaning to structures Orginates from: σηµαντ ικoς (semantikos), significant Orginates from: σηµαινω (semaino), to signify, to indicate

6 The term Semantics Association of meaning to structures Orginates from: σηµαντ ικoς (semantikos), significant Orginates from: σηµαινω (semaino), to signify, to indicate Orginates from: σηµα (sema), sign, mark, token

7 The term In computer science: Meaning of a word in some language Different words of the same language or words from different languages may have the same semantics Meaning not clearly defined

8 The term In computer science: Meaning of a word in some language Different words of the same language or words from different languages may have the same semantics Meaning not clearly defined Connotation

9 The term In computer science: Meaning of a word in some language Different words of the same language or words from different languages may have the same semantics Meaning not clearly defined Connotation Denotation Extensional / Intensional

10 The term Semantic web Web Generally means documents / data on the internet Graph of linked documents Mostly HTML or binary data

11 The term Semantic web Web Generally means documents / data on the internet Graph of linked documents Mostly HTML or binary data Semantic web Association of semantics to documents Association of semantics to links

12 The term Semantic Web initiative Common framework defined by the W3C Mainly includes: RDF, SPARQL and OWL Initiated by Tim Berners-Lee

13 The term Semantic Web initiative Common framework defined by the W3C Mainly includes: RDF, SPARQL and OWL Initiated by Tim Berners-Lee Any other related technologies you want to mention?

14 Outline The term History Expressing semantics Outlook

15 History First version of HTML in 1989 Included markup for documents common at CERN Development focussed on media contents Visual markup HTML used as a presentation layer Application knew document semantics

16 Rationale Amount of documents not discoverable by humans Search engines evolved Answer only trivial questions Which are the capital cities of African countries? The Sematic Web wants to solve this

17 General history HTML UNTANGLE HTML 2.0 SHOE FindUR XML rec. XHTML RDF(S) librdf DAML-ONT / OIL DAML+OIL XML HTML Mar. Nov. Feb. Dec. Mar. Dez. Jun. Oct. Jan. WSDL SWRL GRDDL RuleML WSDL-S SPARQL BPEL4WS RIF meet. OWL 2 Microformats RDFa RDF(S), OWL XML Mar Nov Aug Feb Mar Nov Dez Mar Aug Oct Jun Dec.

18 Current state XHTML 1 and HTML 4 offer document markup: 1 <html> 2 <head> 3 < t i t l e>semantic Web</ t i t l e> 4 <meta name= a u t h o r c o n t e n t= Kore Nordmann /> 5 </ head> 6 <body> 7 <h1>i n t r o d u c t i o n</h1> 8 <p>the term <em>s e m a n t i c web</em> d e s c r i b e s 9 the v i s i o n, t h a t the i n f o r m a t i o n,... </p> 10 </ body> 11 </ html>

19 Visual semantics Common markup still not expressable (shop, forum,..) Humans associate semantics depending on style Elements are misused and styled. Element semantics hard to decide for software

20 Visual semantics Common markup still not expressable (shop, forum,..) Humans associate semantics depending on style Elements are misused and styled. Element semantics hard to decide for software Did you ever misuse HTML elements?

21 Current development XHTML 2 extended document centric markup Removal of deprecated elements (<b>, <i>) Adding structural markup (<section>) Non-semantical markup still existing (<div>, <span>) Countered by (X)HTML 5

22 Current development XHTML 2 extended document centric markup Removal of deprecated elements (<b>, <i>) Adding structural markup (<section>) Non-semantical markup still existing (<div>, <span>) Countered by (X)HTML 5 However, it lacks elements to express the semantics of many of the non-document types of content often seen on the Web. For instance, forum sites, auction sites, search engines, online shops, and the like, do not fit the document metaphor well, and are not covered by XHTML2. Ian Hickson, HTML 5, W3C Working Draft 22 January 2008

23 Outline The term History Expressing semantics Outlook

24 Microformats Reuse (X)HTML class attributes for trivial semantics association 1 <d i v c l a s s= v e v e n t > 2 <span c l a s s= summary >Semantic Web</ span>: 3 <abbr c l a s s= d t s t a r t t i t l e = >March 6 th< / abbr> 4 <abbr c l a s s= dtend t i t l e = >6 th</ abbr>, 5 at <span c l a s s= l o c a t i o n >PHPUG Cologne</ span> 6 </ d i v>

25 Mircroformat standards hcalendar hcard rel (nofollow, license, tag) Votelinks XFN XMDP

26 Mircroformat standards hcalendar hcard rel (nofollow, license, tag) Votelinks XFN XMDP Ever used one of those?

27 Mircroformat critics Very limited set of applications Not extensible (not forward compatible), no namespaces No structural definition, no ontologies May still be the Semantic Web technology

28 Mircroformat critics Very limited set of applications Not extensible (not forward compatible), no namespaces No structural definition, no ontologies May still be the Semantic Web technology HTML, CSS, JavaScript and DOM will be the basic content standards in the foreseeable future. I think evolution on the web will be based on these formats, and this is what WHAT and AJAX do. We will also see a bunch of Microformats being developed, and that s how the semantic web will be built, I believe. Hakon Wium Lie, CTO of Opera Software (2005)

29 RDF Resource Description Form Using (Subject, Predicate, Object) tripels p r e f i x dc : <h t t p : / / p u r l. org / dc / e l e m e n t s /1.1/ >. 2 </b l o g / t h e l o n g w a y t o s e m a n t i c w e b. html> 3 dc : t i t l e The l o n g way to a s e m a n t i c web ; 4 dc : p u b l i s h e r Kore Nordmann.

30 RDF Resource Description Form Using (Subject, Predicate, Object) tripels Links and Resources may be Subject p r e f i x dc : <h t t p : / / p u r l. org / dc / e l e m e n t s /1.1/ >. 2 </b l o g / t h e l o n g w a y t o s e m a n t i c w e b. html> 3 dc : t i t l e The l o n g way to a s e m a n t i c web ; 4 dc : p u b l i s h e r Kore Nordmann.

31 RDF Resource Description Form Using (Subject, Predicate, Object) tripels Links and Resources may be Subject Reification: Object may again a resource p r e f i x dc : <h t t p : / / p u r l. org / dc / e l e m e n t s /1.1/ >. 2 </b l o g / t h e l o n g w a y t o s e m a n t i c w e b. html> 3 dc : t i t l e The l o n g way to a s e m a n t i c web ; 4 dc : p u b l i s h e r Kore Nordmann.

32 RDF usage RDF commonly embedded in XHTML SVG XMP (Extensible Metadata Platform) Usage of any namespace / ontologies 1 <RDF xmlns= h t t p : //www. w3. org /1999/02/22 r d f syntax ns 2 x m l n s : d c= h t t p : // p u r l. org / dc / e l e m e n t s /1.1/ > 3 <D e s c r i p t i o n about= h t t p : // kore nordmann. de > 4 <d c : c r e a t o r>kore Nordmann</ d c : c r e a t o r> 5 < d c : r i g h t s>cc by sa</ d c : r i g h t s> 6 </ D e s c r i p t i o n> 7 </RDF>

33 RDF usage RDF commonly embedded in XHTML SVG XMP (Extensible Metadata Platform) Usage of any namespace / ontologies Who already makes use of RDF? 1 <RDF xmlns= h t t p : //www. w3. org /1999/02/22 r d f syntax ns 2 x m l n s : d c= h t t p : // p u r l. org / dc / e l e m e n t s /1.1/ > 3 <D e s c r i p t i o n about= h t t p : // kore nordmann. de > 4 <d c : c r e a t o r>kore Nordmann</ d c : c r e a t o r> 5 < d c : r i g h t s>cc by sa</ d c : r i g h t s> 6 </ D e s c r i p t i o n> 7 </RDF>

34 Dublin Core Dublin Core Document metadata semantics Not only used with RDF Embeddable in HTML meta tags Developed already 1994 Contains of 15 core elements Additional optional elements

35 RDFa Embed RDF tripels directly in XHtml Still in draft state 1 <d i v x m l n s : d c= h t t p : // p u r l. org / dc / e l e m e n t s /1.1/ > 2 <h2 p r o p e r t y= d c : t i t l e >Das s e m a n t i s c h e Web</h2> 3 <h3 p r o p e r t y= d c : c r e a t o r >Kore Nordmann</h3> 4 </ d i v> Requires a custom XHTML+RDFa-DTD

36 RDFa Embed RDF tripels directly in XHtml Still in draft state 1 <d i v x m l n s : d c= h t t p : // p u r l. org / dc / e l e m e n t s /1.1/ > 2 <h2 p r o p e r t y= d c : t i t l e >Das s e m a n t i s c h e Web</h2> 3 <h3 p r o p e r t y= d c : c r e a t o r >Kore Nordmann</h3> 4 </ d i v> Requires a custom XHTML+RDFa-DTD The authors know of no deployed Web browser that will fail to present an HTML document as intended after adding RDFa markup to the document. However, publishers should be aware that RDFa will not validate in HTML4 at this time. RDFa Primer 1.1

37 Ontologies General representation of semantics Different variants for different semantics Frame-Logics Description-Logics

38 Ontologies General representation of semantics Different variants for different semantics Frame-Logics Description-Logics Basically always consist of: Classes Instances Properties Relations between all those

39 Ontology - Example Classes Ontologies Instances Location countryname: South Africa Country Meronomy Point Of Interest iscityof iscityof iscapitalof cityname: Pretoria City cityname: Cape Town

40 Ontology - Example Classes Ontologies Instances Location countryname: South Africa Country Meronomy Point Of Interest iscityof iscityof iscapitalof cityname: Pretoria City cityname: Cape Town Additionally ontologies may contain axioms Each country has a capital.

41 RDF-Schema What DTD / XML-Schema is to XML, RDF-Schema is to RDF Simple vocabularies, no axioms, no complex inferences 1 <rdf: RDF 2 x m l n s : r d f= h t t p : //www. w3. org /1999/02/22 r d f syntax ns # 3 x m l n s : r d f s= h t t p : //www. w3. org /2000/01/ r d f schema# > 4 5 < r d f s : C l a s s r d f : a b o u t= h t t p : / example. org/#l o c a t i o n > 6 <r d f s : L a b e l>l o c a t i o n</ r d f s : L a b e l> 7 </ r d f s : C l a s s> 8 9 < r d f s : C l a s s r d f : a b o u t= h t t p : / example. org/#c i t y > 10 <r d f s : L a b e l>c i t y</ r d f s : L a b e l> 11 <r d f s : s u b C l a s s O f r d f : r e s o u r c e= #L o c a t i o n /> 12 </ r d f s : C l a s s> 13 </ rdf: RDF>

42 OWL Web Ontology Language (OWL) Extends RDF-Schema with more logical operations Different profiles OWL Lite - Inferences can be calculated in exponential time OWL DL - Matches a popular DL variant, also decidable OWL Full - Superset of RDF-Schema, not decidable

43 OWL Web Ontology Language (OWL) Extends RDF-Schema with more logical operations Different profiles OWL Lite - Inferences can be calculated in exponential time OWL DL - Matches a popular DL variant, also decidable OWL Full - Superset of RDF-Schema, not decidable OWL 2 profiles decidable in PSpace or LogSpace

44 OWL Web Ontology Language (OWL) Extends RDF-Schema with more logical operations Different profiles OWL Lite - Inferences can be calculated in exponential time OWL DL - Matches a popular DL variant, also decidable OWL Full - Superset of RDF-Schema, not decidable OWL 2 profiles decidable in PSpace or LogSpace Can express everything, expressable by frame logics or description logics

45 OWL - example Build class interesting capitals 1 <C l a s s 2 xmlns= h t t p : //www. w3. org /2002/07/ owl 3 x m l n s : r d f= h t t p : //www. w3. org /1999/02/22 r d f syntax ns 4 r d f : I D= C a p t i a l O f I n t e r e s t > 5 <i n t e r s e c t i o n O f> 6 <C l a s s r d f : a b o u t= #C a p i t a l /> 7 <C l a s s r d f : a b o u t= #P o i n t O f I n t e r e s t /> 8 </ i n t e r s e c t i o n O f> 9 </ C l a s s>

46 OWL - example Build class interesting capitals 1 <C l a s s 2 xmlns= h t t p : //www. w3. org /2002/07/ owl 3 x m l n s : r d f= h t t p : //www. w3. org /1999/02/22 r d f syntax ns 4 r d f : I D= C a p t i a l O f I n t e r e s t > 5 <i n t e r s e c t i o n O f> 6 <C l a s s r d f : a b o u t= #C a p i t a l /> 7 <C l a s s r d f : a b o u t= #P o i n t O f I n t e r e s t /> 8 </ i n t e r s e c t i o n O f> 9 </ C l a s s> Just build your ontologies, reasoning is performed by software

47 Query the data Which are the capital cities of African countries? 1 PREFIX my : <h t t p : / / example. org/> 2 SELECT? c a p i t a l 3 WHERE { 4? x my : cityname? c a p i t a l. 5? x my : i s C a p i t a l O f? y. 6? y my : i s I n C o n t i n e n t my : A f r i c a. 7 }

48 Applications Lots of different standards Reuses known stadards like XML and XML-Schema GRDDL will help extracting data from XHTML Triple stores with query support are already implemented: librdf, ARC,

49 Applications Lots of different standards Reuses known stadards like XML and XML-Schema GRDDL will help extracting data from XHTML Triple stores with query support are already implemented: librdf, ARC, Yahoo! SpiderMonkey already actively uses such data

50 Outline The term History Expressing semantics Outlook

51 Bottom line The Semantic Web already emerges Not broad support Entering the Semantic Web is easy with Microformats Custom applications require custom ontologies RDF and OWL will be the major technologies Backed by research

52 Consequence for HTML HTML semantic will get irrelevant Together with CSS pure presentational markup

53 Consequence for HTML HTML semantic will get irrelevant Together with CSS pure presentational markup Documents can be represented by any XML markup (+ Dokbook)

54 Consequence for HTML HTML semantic will get irrelevant Together with CSS pure presentational markup Documents can be represented by any XML markup (+ Dokbook) Wait for CSS3

55 Consequence for HTML HTML semantic will get irrelevant Together with CSS pure presentational markup Documents can be represented by any XML markup (+ Dokbook) Wait for CSS3 Wait for XLink support

56 The end Open questions? Further remarks? Contact Mail: Web: (Slides will be available here soonish)

57 Reference W3C Semantic Web Activity: current state of semantic web.html Semantic Web, Grundlagen, Springer Verlag, ISBN-13:

Standardization of Ontologies

Standardization of Ontologies Kore Nordmann TU Dortmund March 17, 2009 Outline History Related technologies Ontology development General history HTML UNTANGLE HTML 2.0 XML rec. XHTML RDF(S)