Document hierarchy

AtomGraph Processor does not require a specific RDF dataset layout. It includes however a useful one that extends the core AtomGraph Processor vocabulary and uses container/item membership properties from SIOC to describe a resource hierarchy, which is very common in web applications and filesystems.

Dataset

In the dataset, a structure of this wiki could be described like this:

  @base         <https://github.com/AtomGraph/> .

  @prefix gp:	<http://graphity.org/gp#> .
  @prefix foaf: <http://xmlns.com/foaf/0.1/> .
  @prefix sioc:	<http://rdfs.org/sioc/ns#> .

  # webapp root resource
  <> a gp:Container .

  # 1st level container
  <graphity-client> a gp:Container ;
    sioc:has_parent <> .

  # 1st level container
  <graphity-core> a gp:Container ;
    sioc:has_parent <> .

  # 1st level container
  <graphity-processor> a gp:Container ;
    sioc:has_parent <> .

  # 2nd level container
  <graphity-processor/wiki> a gp:Container ;
    sioc:has_parent <graphity-processor> .

  # 2nd level item
  <graphity-processor/wiki/Data-hierarchy> a gp:Document ;
    sioc:has_container <graphity-processor/wiki> .

  # 1st level item
  <graphity-processor/pulse> a gp:Document ;
    sioc:has_container <graphity-processor> .

And so on, deeper down into the container hierarchy where items are leaves - a parent/child relationship just like with folders and files in a file system.

Abstract concepts and physical things

Abstract concepts and things that cannot be directly accessed over HTTP but can still be described in RDF documents can be attached to the document hierarchy using foaf:isPrimaryTopicOf and foaf:primaryTopic properties:

  @base         <https://github.com/AtomGraph/> .

  @prefix foaf: <http://xmlns.com/foaf/0.1/> .
  @prefix doap: <http://usefulinc.com/ns/doap#> .
  @prefix dct:  <http://purl.org/dc/terms/> .
  @prefix xsd:  <http://www.w3.org/2001/XMLSchema#> .

  <> a foaf:Document ;
    foaf:primaryTopic <#project> .

  <#project> a doap:Project ;
    dct:created "2011-09-13"^^xsd:date ;
    foaf:isPrimaryTopicOf <> .

Resource tree

Here the example above is depicted as a resource tree, with resource URIs relative to their parents':

<>
+-- <graphity-client>
+-- <graphity-core>
+-- <graphity-processor>
|   +-- <wiki>
|   |   +-- <Data-hierarchy>
|   +-- <pulse>

All HTTP-accessible resources (which excludes hash URIs such as <graphity-processor#this>) are gp:Documents. By convention, the slashes in the URI structure mark a SIOC parent/children relation in RDF.

Sitemap

In the sitemap ontology, the template for the parent/child relationships is expressed using rdfs:subClassOf and owl:Restrictions. Here is an example from the AtomGraph Processor vocabulary with hierarchy-related properties only:

@base           <http://graphity.org/gp> .

<#Container> a rdfs:Class, owl:Class, <#Template> ;
    rdfs:subClassOf foaf:Document, sioc:Container ,
        [ a owl:Restriction ;
            owl:onProperty sioc:has_parent ;
            owl:allValuesFrom <#Container>
        ] ;
    rdfs:label "Container" ;
    rdfs:comment "Container that can have other containers and items as children" ;
    rdfs:isDefinedBy <#> .

<#Item> a rdfs:Class, owl:Class, <#Template> ;
    rdfs:subClassOf foaf:Document, sioc:Item,
        [ a owl:Restriction ;
            owl:onProperty sioc:has_container ;
            owl:allValuesFrom <#Container>
        ] ;
    rdfs:label "Item" ;
    rdfs:comment "Child item of a container" ;
    rdfs:isDefinedBy <#> .