Named graphs

latest update: 2016-10-25    

Introduction

When triples are stored in a triple store these can be organized in triple sets, also called RDF graphs.

ISO 15926 templates are graphs, consisting of triples that have the URI of the template instance as common subject.

But in cases of patterns or documents, there are sets of templates, and these need some kind of handle. This is where Named Graphs, with a name in the form of a URI, come into play, as detailed below.

A Named Graph can be seen as a kind of "view" on all triples that belong to what is called the Default Graph. The Default Graph is the "universe of discourse", the "supergraph" with the all the information of interest.

Example

An instance of the TIP 'Coating Type' looks like this (characters in red turns it into a Named Graph):

{} # empty default graph

:G0811879F870A479D871E993D485417C6 # graph name

{

:C2738D3A775A548B3B875D11897962CBB rdf:type dm:ClassOfInanimatePhysicalObject, owl:Class ;

    rdfs:subClassOf rdl:RDS736500210 ; # COATING

    meta:valEffectiveDate "2014-08-17T00:00:00Z"^^xsd:dateTime .

:T2F3BFD4F843C419D8451E33DA6541FAF rdf:type tpl:ClassOfFeatureWholePartDefinition, owl:Thing ;

    tpl:hasClassOfWhole :CO_21-P101 ;

    tpl:hasClassOfPart :C2738D3A775A548B3B875D11897962CBB ;

    tpl:hasCardinalityOfWhole rdl:RDS222625 ; # 1:1

    tpl:hasCardinalityOfPart rdl:RDS999900700 ; # 0:*

    meta:valEffectiveDate "2014-08-17T00:00:00Z"^^xsd:dateTime .

:T163969EA57024A2680ED3CA305E87E20 rdf:type tpl:SpecializationOfClassOfIndividual, owl:Thing ;

    tpl:hasSubClass :C2738D3A775A548B3B875D11897962CBB ;

    tpl:hasSuperClass rdl:RDS11857390 ; # EPOXY COATING

    meta:valEffectiveDate "2014-08-17T00:00:00Z"^^xsd:dateTime .

}

All above triples together form a Named Graph by recording theURI of the graph name in column #4 of a quad store.

subject

property

object

graph name

This Graph Name URI can be the subject and/or object of other triples, for example with an overall meta:valEffectiveDate, or other provenance data such as the author, or the originating computer system. Example:

:G0811879F870A479D871E993D485417C6 meta:valEffectiveDate "2014-01-14T00:00:00Z"^^xsd:dateTime .

Any triple may occur in  more than one Named Graph.

Documents

The valve specification, as shown below, has many templates representing its content:

although it remains to be seen that ALL data will be mapped.

All triples, that together represent the information content of this Valve Specification, can be captured by a Named Graph URI. The graph name is the handle to fetch all required information.

Alternatively the template RepresentationOfClassOfIndividualWithTemplateSet can be used plus as many instances of the template EnumerationOfClass as there are template instances to be included. This is explained here in detail.