Submissions:Context Slices

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Current revision ID: 10228

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General information

Name Context Slices
Also known as
Author(s) Chris Welty
SubmittedBy Chris Welty


Motivation Most information on the web is contextualized somehow, for example information may be believed by a person or organization, it may hold only for some time period, it may have been reported/observed by an individual, etc. There are myriad proposals and logics for context, but none are standards and few have even prototype implementations.

In RDF and other binary relation languages (like object oriented languages and description logics), one typical way to represent that a binary relation holds in some context is to "reify" the relation-holding in the context as an node with a binary relations for the subject, object, and property, and a fourth binary relation to the object representing the context itself. The downside to this approach is the expressive ability of the language to describe the binary relation, especially in the case of description logics, is lost. For example, the ancestor relation is transitive. OWL allows one to express transitivity of a binary relation, but this expressiveness is lost if the statements of the relation are reified. The same would be true for symmetry, reflexivity, etc. One can get the effect of cardinality and range/domain restrictions by reifying a relation as an OWL class (instead of using RDF reification), with properties for the roles (as in the n-ary relations W3C note), but not transitivity etc.

The motivation for context slices is to provide a logical pattern for encoding context information in standard RDF graphs that allows some of the expressiveness of OWL to be used in describing the relations that hold in contexts.

This is a generaliztion of the four dimensional ontology for fluents published in [Welty & Fikes, 2006].

Aim To encode that a binary relation holds in a context.
Solution description As shown in the example, the idea of the context slices pattern is, rather than reifying the statement itself, to create a projection of the relation arguments in each context for which some binary relation holds between them.

Take for example the statement "Chris believes Sam is CEO of IBM". Say we already have nodes in some graph representing Sam and IBM.

We create, as shown in the diagram, the context c1 corresponding to Chris' belief, and two nodes representing Chris' belief about Sam and Chris' belief about IBM (shown as Sam@c1 and IBM@c1).

This allows us to represent ceoOf as a binary relation, which seems more natural, and it allows us to use the expressivity of OWL in more ways. We can say of the ceoOf relation that it has an inverse, hasCeo. We can express cardinality, e.g. a company may have only one CEO within a context. We can say that a relation is transitive or symmetric. We can express relation taxonomies in the usual way.

While clearly OWL does not support RDF reification, and so none of this is possible if statement reification is used, as mentioned above a more standard way of representing this kind of information (including time, belief, knowledge, etc.) is to create an OWL class that represents the relation holding, with properties for the arguments. This approach makes it possible to express global but not local range and domain constraints, global but not local cardinality, and symmetry.

Note that the ContextualProjection class should be considered disjoint with any of the classes in an ontology that have projections.

Elements As shown in the diagram, the pattern uses two predefined classes, cs:ContextualProjection and cs:Context. It uses two predefined properties, cs:projectionOf (ContextualProjection x TOP), and cs:hasContext (cs:ContextualProjection x cs:Context). Properties that hold in a context can extend the property cs:contextualProperty.
Implementation In OWL functional syntax:
  Annotation(owl:versionInfo "1.0"@en)
  Annotation(rdfs:label "Context slices ontology logical pattern"@en)

  DisjointClasses(cs:Context cs:ContextualProjection)
  SubClassOf(cs:ContextualProjection ObjectAllValuesFrom(cs:hasContext cs:Context))
  SubClassOf(cs:ContextualProjection ObjectExactCardinality(1 cs:hasContext))
  SubClassOf(cs:ContextualProjection ObjectExactCardinality(1 cs:projectionOf))
  DisjointClasses(cs:ContextualProjection cs:Context)
  ObjectPropertyDomain(cs:contextualProperty cs:ContextualProjection)
  ObjectPropertyRange(cs:contextualProperty cs:ContextualProjection)
  ObjectPropertyDomain(cs:hasContext cs:ContextualProjection)
  ObjectPropertyDomain(cs:projectionOf cs:ContextualProjection)


<?xml version="1.0" encoding="UTF-8"?>
  <!ENTITY owl "">
  <!ENTITY rdf "">
  <!ENTITY rdfs "">
  <!ENTITY xsd "">
<rdf:RDF xml:base=""
  <owl:Ontology rdf:about="">
    <rdfs:label xml:lang="en">Context slices ontology logical  pattern</rdfs:label>
    <owl:versionInfo xml:lang="en">1.0</owl:versionInfo>
  <owl:Class rdf:about="ContextualProjection">
    <rdfs:comment rdf:datatype="&xsd;string">A contextual projection or slice of an entity or event.  
The context defines the contextual extent of the slice.  If any relations hold in a context, they 
must be to other slices of the same context (there is no way to enforce this constraint in OWL).
        <owl:cardinality rdf:datatype="&xsd;nonNegativeInteger">1</owl:cardinality>
        <owl:onProperty rdf:resource="#hasContext"/>
        <owl:cardinality rdf:datatype="&xsd;nonNegativeInteger">1</owl:cardinality>
        <owl:onProperty rdf:resource="#projectionOf"/>
        <owl:allValuesFrom rdf:resource="Context"/>
        <owl:onProperty rdf:resource="#hasContext"/>
    <owl:disjointWith rdf:resource="Context"/>
  <owl:Class rdf:about="Context">
    <rdfs:comment rdf:datatype="&xsd;string">It is intended that this class  should be equated
with whatever class represents contexts, with possibly subclasses for different kinds 
such as BeliefContext, TemporalInterval, etc.</rdfs:comment>
    <owl:disjointWith rdf:resource="#ContextualProjection"/>
  <owl:ObjectProperty rdf:about="#contextualProperty">
    <rdfs:comment rdf:datatype="&xsd;string">A property that holds in a  context.</rdfs:comment>
    <rdfs:domain rdf:resource="#ContextualProjection"/>
    <rdfs:range rdf:resource="#ContextualProjection"/>
  <owl:FunctionalProperty rdf:about="#hasContext">
    <rdf:type rdf:resource="&owl;ObjectProperty"/>
    <rdfs:comment rdf:datatype="&xsd;string">The relation from a  ContextualProjection to the context 
in which some property holds</rdfs:comment>
    <rdfs:domain rdf:resource="#ContextualProjection"/>
  <owl:FunctionalProperty rdf:about="#projectionOf">
    <rdf:type rdf:resource="&owl;ObjectProperty"/>
    <rdfs:comment rdf:datatype="&xsd;string">The entity or event that a  context slice is a slice of.</rdfs:comment>
    <rdfs:domain rdf:resource="#ContextualProjection"/>
Reusable component
Component type


Problem example Here is a simple ontology that extends the logical pattern ontology and represents the statement, "Chris believes Sam is CEO of IBM".
<?xml version="1.0"?>

  <owl:Ontology rdf:about="">
    <rdfs:label xml:lang="en">Example of using context slices</rdfs:label>
    <owl:versionInfo xml:lang="en">1.0</owl:versionInfo>
  <owl:Class rdf:ID="Company"/>
  <owl:Class rdf:ID="Person"/>
  <owl:Class rdf:ID="BeliefContext">
    <rdfs:subClassOf rdf:resource=""/>
  <owl:ObjectProperty rdf:ID="believedBy"/>
  <owl:ObjectProperty rdf:ID="ceoOf">
      <owl:ObjectProperty rdf:ID="contextualProperty"/>

  <Person rdf:ID="Sam"/>
  <Person rdf:ID="Chris"/>
  <Company rdf:ID="IBM"/>

  <BeliefContext rdf:ID="c1">
    <believedBy rdf:resource="#Chris"/>
  <cs:ContextualProjection rdf:about="#IBM$c1">
    <cs:hasContext rdf:resource="#c1"/>
    <cs:projectionOf rdf:resource="#IBM"/>
  <cs:ContextualProjection rdf:about="#Sam$c1">
    <cs:hasContext rdf:resource="#c1"/>
    <ceoOf rdf:resource="#IBM$c1"/>
    <cs:projectionOf rdf:resource="#Sam"/>
Pattern solution example

Pattern reference

Origin This logical pattern is a generalization of the 4D "Reusable Ontology for Fluents in OWL", presented at FOIS-2006.

Welty, Chris and Richard E. Fikes. 2006. A Reusable Ontology for Fluents in OWL. In Bennet and Fellbaum, eds., Proceedings of the Fourth International Conference on Formal Ontology in Information Systems. IOS Press. See

It has been suggestion in Reviews:ValentinaPresutti_about_Context_Slices that this may be a specialization of Submissions:DescriptionAndSituation. The DandS pattern is described in a bit of distributed way across four or so patterns, lacks an example, and uses terms like "description" and "concept" in an unfamiliar way, so I am unable to understand it. The main objective of the CS pattern is to form projections of the objects into the contexts, not the relations, which is I think what DandS does.

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Reviews about Context Slices
Review article Posted on About revision (current is 10228)
VojtechSvatek about Context Slices 245545616 September 2010 1005810,058
EnricoMotta about Context Slices 245545919 September 2010 1011910,119
ValentinaPresutti about Context Slices 245546323 September 2010 1011910,119

This revision (revision ID 10228) takes in account the reviews: ValentinaPresutti about Context Slices

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