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Overview of Resource Description Framework (RFD/XML)

Overview of Resource Description Framework (RFD/XML). Authors:. Date: 2010-11-11. Slide 1. Outline. Basic concept: descriptive statement triple RDF/XML representation RDF capablilities: containers, collections, reification RDF Schema defines application vocabularies

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Overview of Resource Description Framework (RFD/XML)

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  1. Overview of Resource Description Framework (RFD/XML) Authors: Date: 2010-11-11 Slide 1 Joe Kwak (InterDigital)

  2. Outline • Basic concept: descriptive statement triple • RDF/XML representation • RDF capablilities: containers, collections, reification • RDF Schema defines application vocabularies • 802.21 example: RDF Schema for Information Service • References Joe Kwak (InterDigital)

  3. Descriptive Statement property attribute characteristic TRIPLE: Subject | Predicate RDF GRAPH what | | value Truck | color | red created to describe web resources http://www.example.org/index.html has a creator whose value is John Smith <http://www.example.org/index.html> <http://purl.org/dc/elements/1.1/creator> RDF in XML of URIs <http://www.example.org/staffid/85740> . Joe Kwak (InterDigital)

  4. RDF/XML Representation XML qualified names (Qnames) used for RDF shorthand. Common xmlns (xml namespace) prefixes: • prefix rdf:, namespace URI: http://www.w3.org/1999/02/22-rdf-syntax-ns# • prefix rdfs:, namespace URI: http://www.w3.org/2000/01/rdf-schema# • prefix dc:, namespace URI: http://purl.org/dc/elements/1.1/ • prefix owl:, namespace URI: http://www.w3.org/2002/07/owl# • prefix xsd:, namespace URI: http://www.w3.org/2001/XMLSchema# • prefix ex:, namespace URI: http://www.example.org/ • prefix exstaff:, namespace URI: http://www.example.org/staffid/ Same statement using XML prefixes: ex:index.html dc:creator exstaff:85740 . Joe Kwak (InterDigital)

  5. Compound Statements and Blank Nodes Joe Kwak (InterDigital)

  6. Typed Literals • Default literal is string of ascii for URIs • RDF Schema defines many standard datatypes • Online library is commonly referenced • DataTypes defined in library at http://www.w3.org/2001/XMLSchema • "value"^^<DataTypeLibrary # datatypename> Joe Kwak (InterDigital)

  7. DataTypes defined at http://www.w3.org/2001/XMLSchema Joe Kwak (InterDigital)

  8. RDF statements in XML Triple to XML equivalent: Joe Kwak (InterDigital)

  9. More Complex RDF/XML Joe Kwak (InterDigital)

  10. RDF Containers • Bag: items in no significant order • Seq:: items sequenced in a required order • Bag and Seq are semantically identical in XML with <rdf:Bag> - <rdf:Seq> • Application layer needs to interpret order as significant for sequence only • Alt: a set of alternative items "one of the below". Joe Kwak (InterDigital)

  11. Collection is a closed linked list Collection uses property concept of "first", "rest" and defines the null node to delimit list. Collections are closed containers whereas bags and sequences are open. Joe Kwak (InterDigital)

  12. RDF Reification – making the language a thing • Reification permits RDF syntax to be applied to RDF statements. Description of the Description. • RDF triple: • RDF description of the above RDF statement • Useful for provenance descriptors: Created By, Creation Date, Version #etc • These are properties about the code itself • Description NOT about the objects identified and described in the code. Joe Kwak (InterDigital)

  13. RDF permits "Literal" type for XML strings as values • In this example, the value for the book title is an XML string: "" <span xml:lang="en" The <em>&lt;br /&gt;<em> Element Considered Harmful. "" • Note that the string is interpreted as XML and not simply as ascii. Joe Kwak (InterDigital)

  14. RDF Schemas • A Schema is a particular use of rdf_class and rdf_property to define particular terms useful for a particular application • The defined terms are called a VOCABULARY for this RDF application. • The property relationships among the classes are meaningful. • The datatype definitions here are an example of a schema. Joe Kwak (InterDigital)

  15. Customized Schemas are Useful • Custom schema to describe Joe Kwak (InterDigital)

  16. Custom Vehicle Schema in Triples Joe Kwak (InterDigital)

  17. Custom Vehicle Schema in RDF/XML • h Joe Kwak (InterDigital)

  18. Property OBJECT Value has Range of has Domain of Properties of RDF_Properties • RDF language emphasis and some capabilities differ from object oriented languages (OOL). • RDF is a description oriented language (DOL). • In OOL, objects are type classed and they have properties. • In DOL, properties have properties and may be abstractly defined. • Properties have Range and Domain. Joe Kwak (InterDigital)

  19. Examples • Range • Ranges can also be explicit (0..255) • Domain • In a way these RDF statements treat properties like objects Joe Kwak (InterDigital)

  20. Using EPRI's CIM/XML Schema: Joe Kwak (InterDigital)

  21. Issues for 19.1 • Utility of language for describing message structures • Ease of use and readability of language for message structures. • ASN.1 and RDF/XML share most, if not all, features. • Extensibility is key for ASN.1 vs RDF/XML decision. • ASN.1 is tightly structured and requires use of "…" placement to permit extensibility. • RDF allows open ended class and property extensions.There is no "…." construct within RDF. • IN PRACTICE, we would like to know the shortcomings of both approaches. Joe Kwak (InterDigital)

  22. Quick look at 802 standards • 802.11 MIB in ASN.1 • 802.21 Information Service Schema in RDF/XML Joe Kwak (InterDigital)

  23. References • RDF Primer: http://www.w3.org/TR/2004/REC-rdf-primer-20040210/#xmlliterals • RDF Vocabulary Schema: http://www.w3.org/TR/rdf-schema/#ch_domainrange • RDF/XML Schema: http://www.w3.org/TR/xmlschema-1/ andhttp://www.w3.org/TR/xmlschema-2 • Many many others branch out of the above references. Joe Kwak (InterDigital)

  24. Discussion Joe Kwak (InterDigital)

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