The LOM RDF binding – update Mikael Nilsson The Knowledge Management Research Group Centre for user oriented IT design Royal Institute of Technology, Stockholm

Overview ● Background ● Abstract Models (RDF, DC, LOM) ● Issues ● Standard/Recommendation?

Background – Resource Description Framework ● XML – a general markup language – First W3C recommendation final in 1998 – Roots in SGML and HTML ● RDF – a general metadata language – First W3C recommendation final in 1999 – Roots in Descriptive Logic and databases

Background – RDF binding of LOM ● 2001: First draft in IMS Metadata 1.2 – Work by KTH/Stockholm, L3S/Hannover, WU/Vienna, within Edutella and UNIVERSAL ● 2002: PAR accepted for LTSC – Chair: Jon Mason – Second draft based on LOM 1.0 ● 2003 – present: – Ballot-ready rewritten third draft in final stages

Background – binding features ● Reuses DC and Qualified DC vocabulary where appropriate – DC applications able to understand a LOM RDF record partially, without transformation ● Tries to leverage the flexibility of RDF – Easy to combine with other standards / local extensions – Easy to combine several descriptions of the same resource ● See

Background – usage/participation ● The draft LOM RDF binding is is used in several projects – Swedish Educational Broadcasting Company (ur.se) – online digital video archive – Swedish National Agency for Education (5-6 projects) – UK Curriculum Online metadata – UNIVERSAL/EducaNext brokerage platform – Edutella – LOM RSS module (Steven Downes)

Resource Description Framework ● Tim Berners-Lee's vision: A semantic web ● Requirements on RDF: – Metadata Framework (with certain built-in semantics) – Extensible (structurally, but also semantically) – Web-capable (unlike databases / AI systems) – Self-describing (machine semantics)

RDF: Structure ● An RDF description is a set of statements of the form (resource, property, value) ● Let's try to say “This book was written by Mark Twain”. ● A resource can be identified by a URI ● A property is always identified by a URI ● The value is another resource or a string. (urn:isbn: , dc:creator,

RDF: Structure (cont.) ● This framework makes it easy to: – Add new descriptions of the same resource. – Create new properties and use them. – Combine two separate descriptions of one of several resources. ● The result is often drawn as a graph: urn:isbn:... k.Twain dc:creator Mark Twain vCard:FN dcclass:Da te 1886 rdf:type dc:created rdf:value

Vocabularies ● RDF gives you a framework, a grammar. ● The “words” in the language are defined by others (as with XML). ● A vocabulary in the eyes of RDF is a set of URIs ● Every URI must identify something well-defined in the “world” (a thing, a concept, a property, etc.), ● i.e. the URIs must have semantics.

RDF Schema ● W3C has also defined an RDF vocabulary that is intended to be used to describe other RDF vocabularies (such as LOM or DC)! ● RDF Vocabulary Description Language 1.0, also known as RDF Schema. ● RDFS contains a base semantics that is used in alsmost all RDF descriptions. Expresses e.g.: – This resource is a Person – Students are a kind of Persons – “dc:creator” is a Property

DC and RDF abstract models ● Both DC and RDF use a resource – property – value model ● DC has more high-level “values” than RDF – value URIs – value strings – rich values, etc. ● The LOM RDF binding uses the RDF model (of course) ● It also tries to be compatible with the DC model.

What's an Abstract Model? ● Framework for defining “metadata elements” ● Query Languages need a framework – Used in Edutella ● Extensions of both semantic and structural nature ● The LOM AM and DC AM have differences => This is being studied. ● Two/Three models identified (maybe): – Resource/Schema model and Instance model.

Creating an Annotation in LOM/RDF dcterms:W3C DTF lom- ann:Annotation rdf:Al t I thought blablablaen-US Jag tyckte blablablasv-SE ● According to RDF, there are 4 descriptions in this record ● According to DC, there are 2 descriptions (more advanced “value” concept) Annotation description Resource description

DC Resource model ● Essentially resource – property – value –

DC Resource model ● Essence: – Each resource has zero or more properties. – Each property has one or more values. – Each value is a resource (so it can be further described) ● Example: a date can have a string representation, a description, etc.

DC description Model

DC Description Model ● A description is made up of one or more statements about one, and only one, resource. ● Each statement is made up of – a property URI (a URI that identifies a property), – zero or one value URI (a URI that identifies a value of the property), – zero or one encoding scheme URI (a URI that identifies the class of the value), and – zero or more value representations of the value.

The Binding: status ● Includes text and RDF Schemas – Note: RDFS does not do validation! ● Work on the DC AM influences the binding – still not finalized ● General issues: – About schema or about instances? – What is conformance? ● Paper on the binding at ARIADNE conference 2003:

The Binding: contents ● Conceptually, two things (recent insights): – A list of URIs, and their associated semantics. ● Can be partially encoded in an RDF Schema ● Nothing related to constraints ● This is 100% normative – A specification of constraints for their use ● Multiplicity, ordering, nesting, use of DC vocab, etc. ● All the constraints of the schema ● This part cannot be normative. Why?

The Binding ● Why cannot the constraints part be normative? – No control over record boundaries, orcombinations of descriptions – Interferences with external vocabularies (DC, vCard) – In short: conformance is not well-defined. ● Possibilities: – One Standard, normative/informative parts – One Standard, One Recommended Practice – One Recommended practice.

The Binding: misc ● Note that there are two RDF specs: – Concepts and abstract syntax – RDF/XML syntax ● The binding will not use XML RDF syntax, only graphs, and maybe a notation called N3, (used for RDF testcases). – Unfortunately, the RDF/XML syntax is confusing both for RDFers and non-RDFers.

Summary ● Abstract Model work closely related ● Standard/Recommendation? ● No XML in binding.