The Semantic Web Matt Klubertanz
What is it? • “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)
What will be covered • A little history • Semantic Web growth • The three foundations • RDF • OWL • SPARQL • Demo of SPARQL query
History • Late 1989 Tim Berners-Lee proposed the idea of HyperText Transfer Protocol (HTTP) and is credited with inventing the World Wide Web • In 1994 Tim Berners-Lee founded the W3C (World Wide Web Consortium) • In 1999 W3C gains interest in creating a new web. Tim Berners-Lee gives it the name “Semantic Web” • W3C has been developing standards involved in the Semantic Web since.
Semantic Web Growth • Over the past few years the Semantic Web has really been picking up momentum • The amount of data being linked in the Semantic Web has been growing exponentially
Linking Open Data cloud diagram, by Richard Cyganiak and AnjaJentzsch. http://lod-cloud.net/
Linking Open Data cloud diagram, by Richard Cyganiak and AnjaJentzsch. http://lod-cloud.net/
Linking Open Data cloud diagram, by Richard Cyganiak and AnjaJentzsch. http://lod-cloud.net/
Linking Open Data cloud diagram, by Richard Cyganiak and AnjaJentzsch. http://lod-cloud.net/
DBpedia • Is structured data from Wikipedia • Has become basically the central hub for the Semantic Web • According to DBpedia it has a knowledge base that currently describes 4 million things • They also say that they have about 2.46 billion RDF triples
RDF • Stands for Resource Description Framework • Framework for describing data on the Semantic Web • Uses URI’s (Universal Resource Identifier) • URL’s are a type of URI • So an identifier in RDF could use a URL • Ex. • I could use http://www.somesite.com/people/about/Mattto refer to any data about myself
RDF cont. • RDF is written in XML • RDF uses statements or triples to describe data • Subject • Predicate • Object • Simple Example • <?xml version="1.0"?><RDF> <Description about="http://www.somesite.com/rdf"> <person>Matt Klubertanz</person> <location>Platteville</location> </Description></RDF>
OWL • Stands for Web Ontology Language • Built on top of RDF • Adds the following to RDF according to W3C • “Ability to be distributed across many systems” • “Scalability to Web needs” • “Compatibility with Web standards for accessibility and internationalization” • “Openness and extensibiltiy” • Basically adds more vocabulary on top of RDF
SPARQL • A language used to perform RDF queries • Used to get data from the Semantic Web • Uses the RDF triples to preform the queries • SPARQL 1.0 was the official recommendation of the W3C in 2008 • Then in March of 2013 the official recommendation became SPARQL 1.1 • SPARQL 1.1 added features like subqueriesand negation as well as expanded the set of functions and operators
SPARQL structure #prefix declarations of URIs PREFIX prop: http://somesite.com/properties/ ... SELECT ... WHERE { ... } ORDER BY ...
Example of SPARQL PREFIX type: <http://dbpedia.org/class/yago/> PREFIX prop: <http://dbpedia.org/property/> SELECT ?country_name ?population WHERE { ?country a type:LandlockedCountries ; rdfs:label?country_name ; prop:populationEstimate?population . FILTER (?population > 15000000 && langMatches(lang(?country_name), "EN")) . } ORDER BY DESC(?population)
Built in Functions • Logical: • !, &&, || • Math: • +, -, *, / • Comparison: • =, !=, >, <, IN, NOT IN... • SPARQL tests: • isURI, isBlank, isLiteral, isNumeric, bound • SPARQL accessors: • str, lang, datatype • Other: • sameTerm, langMatches, regex, REPLACE • Conditionals (SPARQL 1.1): • IF, COALESCE, EXISTS, NOT EXISTS • Constructors (SPARQL 1.1): • URI, BNODE, STRDT, STRLANG, UUID, STRUUID
Built in Functions cont. • Strings (SPARQL 1.1): • STRLEN, SUBSTR, UCASE, LCASE, STRSTARTS, STRENDS, CONTAINS, STRBEFORE,STRAFTER, CONCAT, ENCODE_FOR_URI • More math (SPARQL 1.1): • abs, round, ceil, floor, RAND • Date/time (SPARQL 1.1): • now, year, month, day, hours, minutes, seconds, timezone, tz • Hashing (SPARQL 1.1): • MD5, SHA1, SHA256, SHA384, SHA512
Running SPARQL queries • http://dbpedia.org/sparql
References • Berners-Lee, Tim. "Tim Berners-Lee: The next Web." Lecture. TED. Mar. 2009. Web. <http://www.ted.com/talks/tim_berners_lee_on_the_next_web.html>. • Feigenbaum, Lee, and Eric Prud'hommeaux. "SPARQL by Example - Cambridge Semantics." Cambridge Semantics. N.p., 30 May 2013. Web. 23 Sept. 2013. <http://www.cambridgesemantics.com/semantic-university/sparql-by-example>. • Hori, Masahiro, JérômeEuzenat, and Peter F. Patel-Schneider. "OWL XML Syntax: OWL Examples in XML Syntax." W3C. N.p., 11 June 2003. Web. 23 Sept. 2013. <http://www.w3.org/TR/owl- xmlsyntax/apd-example.html>. • Prud'hommeaux, Eric, and Andy Seaborne. "SPARQL Query Language for RDF." SPARQL Query Language for RDF. N.p., 15 Jan. 2008. Web. 23 Sept. 2013. <http://www.w3.org/TR/rdf-sparql- query/>. • Wang, Xia, and Wolfgang A. Halang. Discovery and Selection of Semantic Web Services. Heidelberg: Springer, 2013. Print. • Crowther, Rob. "Planning a Semantic Web Site." Planning a Semantic Web Site. N.p., 10 Apr. 2008. Web. 11 Nov. 2013. • Cyganiak, Richard and JentzschAnja. Linking Open Data cloud diagram. 28 Sept. 2013 http://lod-cloud.net/
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