RDF WG Update SemTechBiz 2012


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RDF WG Update SemTechBiz 2012

  1. 1. David Wood Updating RDF co-chair, W3C RDF Working Group June 2012Wednesday, May 30, 12
  2. 2. Charter •Define RDF 1.1 •Break as little as possible. •Reflect real-world experiences back into the standards. http://www.w3.org/2011/rdf-wg/Wednesday, May 30, 12
  3. 3. Out of Scope •Changing the fundamentals of RDF(S) semantics •Removing current restrictions in the RDF model (e.g., literals not allowed as subjects, or blank nodes as predicates)Wednesday, May 30, 12
  4. 4. Comment RDF is the data model; More standard serializations will help show that.Wednesday, May 30, 12
  5. 5. Documents • RDF 1.1 Concepts and • (New) Turtle Abstract Syntax • (New) N-triples • RDF 1.1 Semantics • (New) JSON-LD • RDF 1.1 Primer • (Minor changes) RDF/XML Syntax Specification • (Minor changes) RDF Vocabulary Description Language 1.1: RDF SchemaWednesday, May 30, 12
  6. 6. RD FW G X Oh, hey, I didn’t Can we just change see you guys all Who’s the spec so I can Everything can Graphs can’t be labile the way over there that? be a resource implement it? and I’m not either Users Web Framework RESTifarians Logicians Mathematicians Coders CodersThanks and apologies to xkcdWednesday, May 30, 12
  7. 7. e r s a i m s cl D iWednesday, May 30, 12
  8. 8. Progress •Turtle, First Public Working Draft, 2011-08-09 •RDF 1.1 Concepts and Abstract Syntax, First Public Working Draft, 2011-08-30 •XSD 1.1 usage •Lots of lessons learned regarding use cases, concerns and expectations.Wednesday, May 30, 12
  9. 9. Progress •Current list of resolutions: http://demo.3roundstones.net/rdf/2012/rdfwg/ resolutions.xhtml?view •Closed issues: http://www.w3.org/2011/rdf-wg/track/issues/ closedWednesday, May 30, 12
  10. 10. Challenges •Graphs •Charter: “Standardize a model and semantics for multiple graphs and graphs stores” •This is the most contentious portion of our work because it has the potential to radically change RDF, which we are not chartered to do.Wednesday, May 30, 12
  11. 11. Graphs •A “Graph Container” is a container, like a mutable “set” data structure in programming. It holds some RDF triples. •An “RDF Graph” is an idealized snapshot of a Graph Container; its a mathematical set of RDF triples. •A “Graph Serialization” is a particular sequence of characters or bytes which conveys a particular RDF Graph in a language (e.g. Turtle or JSON-LD).Wednesday, May 30, 12
  12. 12. Blank Nodes •Many RDF users avoid using blank nodes. In some circles, this is considered to be a best practice. •Some issues raised by the use of blank nodes are how they may be followed (e.g. in SPARQL result sets) or referenced (e.g. within the same RDF document). •Optionally Skolemize blank nodes when desired.Wednesday, May 30, 12
  13. 13. Blank Nodes • In situations where bNode identification is needed, systems may systematically transform some or all of the blank nodes in an RDF graph into new, globally unique IRIs (Skolem IRIs). • For example, the authority responsible for the domain example.com could mint the following recognizable Skolem IRI: http://example.com/.well-known/genid/ d26a2d0e98334696f4ad70a677abc1f6 • Makes bNodes useful in the same way that auto_increment columns in SQL are.Wednesday, May 30, 12
  14. 14. New Datatypes • Added new RDF-compatible XSD 1.1 datatypes: • xsd:duration • xsd:dayTimeDuration • xsd:yearMonthDuration • xsd:dateTimeStampWednesday, May 30, 12
  15. 15. String Literals •All literals are typed. “Typed literal” becomes redundant. •“foo” becomes syntactic sugar for “foo”^^xsd:string. • Systems SHOULD silently convert xsd:string data to plain literals on output. • The RDF WG is recommending to the SPARQL WG and other SemWeb WG’s that they do the same. • Literals with a language tag now have the datatype IRI rdf:langString.Wednesday, May 30, 12
  16. 16. rdf:XMLLiteral •XMLLiterals will be optional. •The lexical space consists of well-formed XML fragments. •The canonical lexical form is http://www.w3.org/TR/ xml-exc-c14n/, as defined in RDF 2004 (no longer requires lexical forms to be canonicalized). •The value space consists of a set of DOM4 DocumentFragment nodes.Wednesday, May 30, 12
  17. 17. rdf:HTML •rdf:HTML literals will be introduced. •The lexical space consists of the set of Unicode strings. •The value space consists of a set of DOM4 DocumentFragment nodes. •Two DocumentFragment nodes A and B are considered equal if and only if the DOM4 method A.isEqualNode(B) returns true.Wednesday, May 30, 12
  18. 18. New RDF Serializations •Turtle: •Changed very little. •Turtle / SPARQL syntax harmonisation •N-Triples: •Orginally defined only for RDF test cases, n-triples will be standardized primarily for use as a bulk loading syntax. •JSON-LD (probably)Wednesday, May 30, 12
  19. 19. (Minor) Changes to Turtle •ISSUE-1: Turtle / SPARQL harmonization •‘.’s and ‘:’ in names in all positions of a local name apart from the first or last, e.g. ex:first.name / ns:foo:bar •Escape characters in prefixed names, e.g. ex:resource/thing123 / ex:thing123#this •Digits in the first character of local names, e.g. ex:7tmWednesday, May 30, 12
  20. 20. (Minor) Changes to Turtle •Floats require a decimal after the ‘.’, e.g. ex:subject ex:hasValue “18.0” . (so you no longer need a space before the trailing ‘.’) •Adopted case-sensitive constants for xsd:boolean true and false.Wednesday, May 30, 12
  21. 21. (Minor) Changes to Turtle •At risk feature: •SPARQL: PREFIX dc: <http://purl.org/dc/terms/> •Turtle: @prefix dc: <http://purl.org/dc/terms/> . or prefix dc: <http://purl.org/dc/terms/> (case insenstive, like SPARQL)Wednesday, May 30, 12
  22. 22. Turtle •HTML5: <script type="text/turtle"> @prefix frbr: <http://purl.org/vocab/frbr/core#> . <http://books.example.com/works/45U8QJGZSQKDH8N> a frbr:Work . </script> •XHTML: <script type="text/turtle"> # <![CDATA[ @prefix frbr: <http://purl.org/vocab/frbr/core#> . <http://books.example.com/works/45U8QJGZSQKDH8N> a frbr:Work . # ]]> </script>Wednesday, May 30, 12
  23. 23. N-triples •Now UTF-8 •Shifted to IRIs, not RDF URI References •Media type: application/rdf-triples •Tied closely to the Turtle grammarWednesday, May 30, 12
  24. 24. JSON-LD •JSON-LD developed away from the RDF WG, now back (see http://json-ld.org) •JSON-LD is a language capable of serializing any RDF graph, and performing full RDF to JSON-LD to RDF round-tripping. •Working Draft stage, but more mature than most (e.g. implementations exist) •Concerns: (Perceived lack of WG JS knowledge)Wednesday, May 30, 12
  25. 25. JSON-LD { "@context": "http://json-ld.org/contexts/person", "@id": "http://dbpedia.org/resource/John_Lennon", "name": "John Lennon", "birthday": "10-09", "member": "http://dbpedia.org/resource/The_Beatles" }Wednesday, May 30, 12
  26. 26. The RDF Working Group is: Jean-François Baget Fabien Gandon Nathan Rixham Thomas Baker Charles Greer Guus Schreiber Adrien Basse Alex Hall Andy Seaborne Scott Bauer Steve Harris Manu Sporny Aidan Boran Michael Hausenblas Thomas Steiner Dan Brickley Sandro Hawke Mouhamadou Thiam Matteo Brunati Patrick Hayes Ted Thibodeau Gaoussou Camara Ivan Herman Thomas Visel Gavin Carothers Nicholas Humfrey William Waites Jeremy Carroll Kingsley Idehen Jan Wielemaker Pierre-Antoine Champin Arnaud Le Hors David Wood Kiu Ching Dickson Lukose Zhe Wu Olivier Corby Ivan Mikhailov Mohamed Zergaoui Richard Cyganiak Peter Patel-Schneider Antoine Zimmermann Souripriya Das Eric Prudhommeaux Lee Feigenbaum Yves RaimondWednesday, May 30, 12
  27. 27. David Wood Updating RDF co-chair, W3C RDF Working Group June 2012Wednesday, May 30, 12