Vocabulary File Structure

A vocabulary declared in RDF/XML format contains three sections: the prolog, the content header, and the content itself.

This page discusses:

See Also
Constraining Property Range with Enumerated Values
Translation
Basic RDF and OWL Elements
About RDF/OWL Vocabulary Concepts

Prolog

The prolog includes information that applies to the whole document such as the XML version, the character encoding, and the document structure.

  • The xml version must be the first line in the document and no other content or white space can precede it.
  • The encoding declaration must appear immediately after the version information in the XML declaration.
  • The DOCTYPE declaration allows you to identify the root element of the document and the related document type definition (DTD) by referencing an external file, through direct declarations, or both. A DOCTYPE declaration can contain:
    • The name of the root element. This is mandatory when using the DOCTYPE declaration.
    • A subset of DTD direct declarations listed between brackets ([ ]). Each declaration is an ENTITY definition with the prefix string of a namespace that refers to an external vocabulary content. This is to reuse the terms or elements of the external vocabulary in the current vocabulary (acts like a C/C++ #include statement).

Prolog Declaration Example



Vocabulary Header

The vocabulary header starts with the root element <rdf: RDF> and the list of namespace declarations to use, with their prefixes.

Vocabulary Header Declaration Example



In this declaration, you have:

  • The prefixes of all external vocabulary namespace to use in the defined vocabulary. Some are from standards like RDF and OWL, and one from DS, the ds6w vocabulary.
  • The base namespace of the defined vocabulary.
  • ds6w: Prefix used in the vocabulary to reference resources from the ds6w vocabulary.
  • http:**www.3ds.com/vocabularies/pno/: Namespace of the vocabulary.
  • pno: Short name of the vocabulary (pno) also used as prefix.

Vocabulary Content

Define the vocabulary content as an ontology. To declare a new vocabulary, use the <owl:ontology> element, and declare the following attributes.

Attribute Description
rdf:about Specify the unique name of the vocabulary by giving its URI. The URI fragment is also used to give a human-readable name to the vocabulary.

This name must be the same as the prefix declared in the header. In the example below, the short name of the vocabulary defined is pno.

rdfs:label Specify the NLS translation name of the vocabulary for a given language.
rdfs:comment Give a short description of the vocabulary.
owl:versionInfo Specify the release number of the vocabulary.

Vocabulary Content Declaration Example



In this example, you have:

  • My Testing Vocabulary: A human-readable name for the vocabulary.
  • http:/www.3ds.com/vocabularies/sdm/: URI of this vocabulary (unique name). It must end with /
  • sdm: Name of the vocabulary to use as the namespace prefix.
  • 2015x: Version number of this vocabulary.
  • This ontology aims at testing: Short description of the vocabulary.
Tip: Use short names and lowercase letters when assigning a name to the vocabulary.

Define a Predicate

This topic explains how to define a predicate or property.

There are different constructs to define a predicate or property:

  • In RDF, use rdf:Property to link an individual (instance or a class) to another individual or a data value (or a literal).
  • In OWL, you have two types of properties:
    • owl:ObjectProperty to link individuals to individuals. The value type is a class as values are objects.
    • owl:DatatypeProperty to link individuals to data values (literal).
      Important: Use owl:DatatypeProperty to declare:
      • 6WTags as they are always literals. For example, string xsd:string, integer xsd:integer, boolean xsd:boolean, etc.
      • Ranges (rdfs:range).


To specify where to classify tags against 6W root properties (What, When, Where, Who, Why, How), use rdfs:subPropertyOf.

Important: Any custom 6W property must have an rdfs:subPropertyOf statement set to a 6W root property. If you do not define this statement or set it to another property than a 6W root, the import of the whole RFD/XML file fails.

Predicate Declaration Example



In this example, a ds6w property is defined as the instance of the owl:DatatypeProperty class.

This property is the subproperty of the where 6W root property and has the following characteristics:

  • station: Local name of the predicate. URI is then sdm:station (where sdm is the prefix of the ontology.)
  • Station: Human-readable name of the predicate with a language tag (en)
  • rdfs:subPropertyOf: Used to classify tags associated with Station under 6W root property Where (ds6w:where).
  • rdfs:range: Indicates the basic type of the property, which must be one of the following: &xsd;string, &xsd;integer, &xsd;Boolean, &xsd;dateTime, or &xsd;double.

Tips:
  • Use lowercase characters for predicate names (camel case if many words), for example representedBy.
  • Use a verb to name ObjectProperty, for example implements.
  • Use a noun to name DatatypeProperty, for example status.