The Property Reification Vocabulary 0.11

Status of This Document

The Property Reification Vocabulary is design after a proposal made by Jiří Procházka, Richard Cyganiak and Toby Inkster and extended by Bob Ferris. It should reflect the important use case and ontology design pattern of property reification, which is different from statement reification (see also background and this explanation). This gives ontology designers the freedom to separate such property reification definitions from their core ontology and enable hence the opportunity to make them optional.
The template of this specification is derived from the FOAF Vocabulary Specification, which was created by Dan Brickley and Libby Miller, and the Music Ontology Specification, which was created by Yves Raimond. It was modified and extended by Bob Ferris. Furthermore, a modified and extended version of Danbri's SpecGen version was used to generate most of the RDFa statements of the Property Reification Vocabulary for this specification (see here for SpecGen version 6 by Bob Ferris).

This document is created by combining the RDFS/OWL machine-readable Property Reification Vocabulary with a human-readable HTML representation that includes RDFa annotations. Future versions may incorporate multilingual translations of term definitions. The RDF/XML version of the specification is also available directly from the namespace URI. RDF/N3 representations could be access via the links above.

The authors welcome comments on this document, preferably via the author's email addresses.

Table of Contents

• The Property Reification Vocabulary at a glance
• Examples
• Introduction
• What's the Property Reification Vocabulary for?
• Background
• The Property Reification Vocabulary and Standards
• Evolution and Extension of the Property Reification Vocabulary
• The Property Reification Vocabulary cross-reference: Listing the Property Reification Vocabulary Classes and Properties
• External Vocabulary References
• Acknowledgments
• Recent Changes

The Property Reification Vocabulary at a glance

The prv:PropertyReification concept as graph with relations:

An a-z index of Property Reification Vocabulary terms, by class (categories or types) and by property.

Examples

• A Simple Example
• Cognitive Characteristic Ontology Example

A Simple Example

RDF/Turtle representation of a simple property reification definition example created with help of the Property Reification Vocabulary (see also RDF and N3 for downloadable representations of this example) that includes also an example of its application:

@prefix prv: <http://purl.org/ontology/prv/core#> .
@prefix xsd: <http://www.w3.org/2001/XMLSchema#> .
@prefix ex:  <http://example.org/> .
 
ex:ReadReification a prv:PropertyReification ;
   prv:shortcut ex:hasRead ;
   prv:reification_class ex:ReadingEvent ;
   prv:subject_property ex:reader ;
   prv:object_property ex:book .
 
# The quick way
<#alice> ex:hasRead <#beekeeping> .
 
# The detailed way
<#myreadingevent> a ex:ReadingEvent ;
   ex:reader <#alice> ;
   ex:book <#beekeeping> ;
   ex:when "2010-11-01"^^xsd:date .

In the example above one can see a property reification definition that utilize some temporarily defined terms and an example of its application. The example includes a property reification definition for the shortcut relation property ex:hasRead. Thereby, this property reification definition utilizes the reification class ex:ReadingEvent. Furthermore, the subject property is ex:reader and the object property is ex:book.
Due to the property reification definition from above and the shortcut relation and property reification rules (see here) one can clearly reason that the shortcut relation (see "The quick way") and reification class instance (see "The detailed way") in the example are belonging semantically together. The detailed description is additionally associated with a date (ex:when), that represents when the person (<#alice>) read the book (<#beekeeping>).
The property reification definition of this example makes especially use of the reification class (prv:reification_class) to utilize a reification class and a shortcut relation property (prv:shortcut) as identification terms to establish the semantic relation between a shortcut relation and its belonging reification class instance(s).

Cognitive Characteristics Ontology Example

RDF/Turtle representation of a property reification definitions example of the Cognitive Characteristics Ontology created with help of the Property Reification Vocabulary (see also RDF and N3 for downloadable representations of this example):

@prefix prv: <http://purl.org/ontology/prv/core#> .
@prefix cco: <http://purl.org/ontology/cco/core#> .
@prefix ex:  <http://example.org/> .
 
ex:SkillReification a prv:PropertyReification ;
   prv:shortcut cco:skill ;
   prv:shortcut_property cco:characteristic ;
   prv:reification_class cco:CognitiveCharacteristic ;
   prv:subject_property cco:agent ;
   prv:object_property cco:topic .
 
ex:ExpertiseReification a prv:PropertyReification ;
   prv:shortcut cco:expertise ;
   prv:shortcut_property cco:characteristic ;
   prv:reification_class cco:CognitiveCharacteristic ;
   prv:subject_property cco:agent ;
   prv:object_property cco:topic .
 
ex:InterestReification a prv:PropertyReification ;
   prv:shortcut cco:interest ;
   prv:shortcut_property cco:characteristic ;
   prv:reification_class cco:CognitiveCharacteristic ;
   prv:subject_property cco:agent ;
   prv:object_property cco:topic .
 
ex:BeliefReification a prv:PropertyReification ;
   prv:shortcut cco:belief ;
   prv:shortcut_property cco:characteristic ;
   prv:reification_class cco:CognitiveCharacteristic ;
   prv:subject_property cco:agent ;
   prv:object_property cco:topic .
 
ex:SettingReification a prv:PropertyReification ;
   prv:shortcut cco:setting ;
   prv:shortcut_property cco:characteristic ;
   prv:reification_class cco:CognitiveCharacteristic ;
   prv:subject_property cco:agent ;
   prv:object_property cco:topic .

In the example above one can see property reification definitions that utilize terms of the Cognitive Characteristics Ontology. The example includes property reification definitions for the shortcut relation properties cco:skill, cco:expertise, and cco:interest. Thereby, every property reification definition utilizes the same reification class, cco:CognitiveCharacteristic. Furthermore, also the subject and object property are in every definition the same, cco:agent (as subject property) and cco:topic (as object property).
Due to the property reification definitions from above and the shortcut relation and property reification rules (see here) one can clearly reason that the shortcut relations and reification class instances in the soccer example of the Cognitive Characteristics Ontology are belonging semantically together (here pairwise).
The property reification definitions of this example make especially use of the shortcut property (prv:shortcut_property) to utilize a reification class for several shortcut relation properties (property reification definitions). Finally, these definitions are described in the Cognitive Characteristics Ontology - Property Reification Mappings.

Introduction: Property Reification Vocabulary Basics

The graphic above illustrates the prv:PropertyReification concept and its related properties as extension of RDFS. It associates

• the reification class (prv:reification_class),
• the property of the shortcut relation (prv:shortcut),
• the shortcut property (prv:shortcut_property), that means, the property that relates to the property of the shortcut relation in reification class instances,
• the subject property (prv:subject_property), that means, the property that relates to a subject of the shortcut relation in reification class instances, and
• the object property (prv:object_property), that means, the property that relates to a object of the shortcut relation in reification class instances,

of a property reification definition. This design provides the opportunity to utilize a reification class for several property reification definitions. That means, at least also for several shortcut relation definitions (properties), due to a matching between the shortcut relation property defined in a property reification definition by prv:shortcut and the associated shortcut relation property by the shortcut property (prv:shortcut_property) in a reification class instance.

What's the Property Reification Vocabulary for?

The Property Reification Vocabulary should enable a reasoning engine to apply the following implications, which are represented as N3 rules (see also shortcut relation rule and property reification rule for downloadable representations of these rules):

@prefix prv: <http://purl.org/ontology/prv/core#> .
 
{
   ?pr a prv:PropertyReification ;
      prv:shortcut ?sc ;
      prv:reification_class ?rc ;
      prv:shortcut_property ?scp ;
      prv:subject_property ?sp ;
      prv:object_property ?op .
 
   ?r a ?rc ;
      ?scp ?sc ;
      ?sp ?s ;
      ?op ?o .
}
=>
{ ?s ?sc ?o } .

The shortcut relation rule above means, if a prv:PropertyReification instance ?pr exists, which includes

• the shortcut relation property ?sc (associated by prv:shortcut),
• and an instance of a reification class ?rc (associated by prv:reification_class of the prv:PropertyReification instance ?pr) exists, where
  • the shortcut relation prediate ?sc is associated by the definied shortcut property ?scp (associated by prv:shortcut_property of the prv:PropertyReification instance ?pr),
  • the shortcut relation subject ?s is associated by the defined subject property ?sp (associated by prv:subject_property of the prv:PropertyReification instance ?pr) and
  • the shortcut relation object ?o is associated by the defined object property ?op (associated by prv:object_property of the prv:PropertyReification instance ?pr),

then a shortcut relation can be constructed, which has

• as its subject the particular ?s,
• as its predicate the property ?sc and
• as its object the particular ?o.

@prefix prv: <http://purl.org/ontology/prv/core#> .
 
{ 
   ?s ?sc ?o .

   ?pr a prv:PropertyReification ;
      prv:shortcut ?sc ;
      prv:reification_class ?rc ;
      prv:shortcut_property ?scp ;
      prv:subject_property ?sp ;
      prv:object_property ?op .
}
=>
{
   ?r a ?rc ;
      ?scp ?sc ;
      ?sp ?s ;
      ?op ?o .
} .

The property reification rule above means, if a shortcut relation exists, which has

• as its subject the particular ?s,
• as its predicate the property ?sc and
• as its object the particular ?o,

and a prv:PropertyReification instance ?pr exists, which relates

• the shortcut relation property ?sc (associated by prv:shortcut),
• the reification class ?rc (associated by prv:reification_class
• the shortcut property ?scp (associated by prv:shortcut_property),
• the subject property ?sp (associated by prv:subject_property) and
• the object property ?op (associated by prv:object_property,

then an instance ?r of a reification class ?rc can be constructed, which relates

• the shortcut relation prediate ?sc (associated by the definied shortcut property ?scp),
• the shortcut relation subject ?s (associated by the defined subject property ?sp) and
• the shortcut relation object ?o (associated by the defined object property ?op).

With help of the property reification and shortcut relation rule a reasoning engine should not only be able to infer (construct) related representations, but also to reason that existing shortcut relations and instances of reification classes belonging semantically together.
Both rules are also described with help of SPIN (SPARQL Inferencing Notation) and are available via the namespace URI 'http://purl.org/ontology/prv/rules#'. Thus, one can directly retrieve a description of the property reification rule and the shortcut relation rule and use these descriptions to feed a reasoning engine.

Background

It seems that there is still a lack in modelling contextual information for Semantic Graph triples and deploying this knowledge representation reusable in a distributed Linked Data environment. Although, there exists probably applicable solutions for representing external context*, e.g. Named Graphs or N-Quads. However, these methods are not really appropriated to represent internal context* by keeping clear semantics regarding their described Semantic Graph triples (information resource). Even the existing method for RDF statements, RDF Reification (statement reification), has no clear semantics between the statement triple(s) and their reification information resource(s). Furthermore, this method is intended to be applied at the instance level. Although, it might be good to be able to apply reification definition also on the vocabulary level. That means, to reify the semantic relation that is established by a property. This kind of reification is then called property reification.
Therefore, the simple semantic relation, represented by subject, predicate and object, is now defined as shortcut relation. Thereby, the predicate is always the same property for a single shortcut relation definition. Beyond, the class that enables a detailed description of such a n-ary relation is called reification class.
Due to the reason, that there wasn’t a published vocabulary that addresses a mapping and its semantics between shortcut relations and reification classes and vice versa, Bob Ferris co-designed the Property Reification Vocabulary. This vocabulary is designed after a proposal made by Jiří Procházka, Richard Cyganiak and Toby Inkster and was also extended by Bob Ferris to enable further functionality. It should reflect the important use case and ontology design pattern of property reification. This gives ontology designers the freedom to separate such property reification definitions from their core ontology definition and enable hence the opportunity to make them optional.

*) see "Understanding Data by their Context Using RDF" [Tolle, Karsten; 2004] for a definition of external and internal context

The Property Reification Vocabulary and Standards

TODO

TODO

The Property Reification Vocabulary Description

This specification serves as the Property Reification Vocabulary "namespace document". As such it describes the Property Reification Vocabulary and the terms (RDF classes and properties) that constitute it, so that Semantic Web applications can use those terms in a variety of RDF-compatible document formats and applications.

This document presents the Property Reification Vocabulary as a Semantic Web vocabulary or Ontology. The Property Reification Vocabulary is pretty simple, pragmatic and designed to allow simultaneous deployment and extension. The Property Reification Vocabulary is intended for widescale use, but its authors make no commitments regarding its suitability for any particular purpose.

Evolution and Extension of the Property Reification Vocabulary

The Property Reification Vocabulary is identified by the namespace URI 'http://purl.org/ontology/prv/core#'. Revisions and extensions of the Property Reification Vocabulary are conducted through edits to this document, which by convention is accessible in the Web via the namespace URI. For practical and deployment reasons, note that we do not update the namespace URI as the vocabulary matures.

The evolution of the Property Reification Vocabulary is best considered in terms of the stability of individual vocabulary terms, rather than the specification as a whole. As terms stabilise in usage and documentation, they progress through the categories 'unstable', 'testing' and 'stable'. Older terms are marked 'archaic' which allows the possibility of older forms to become modern again.