3.3.9 Predicate properties

The predicates below form an experimental interface to provide more reasoning inside the kernel of the rdb_db engine. Note that symetric, inverse_of and transitive are not yet supported by the rest of the engine. Also note that there is no relation to defined RDF properties. Properties that have no triples are not reported by this predicate, while predicates that are involved in triples do not need to be defined as an instance of rdf:Property.

[det]rdf_set_predicate(+Predicate, +Property)

Define a property of the predicate. This predicate currently supports the following properties:

symmetric(+Boolean)

Set/unset the predicate as being symmetric. Using symmetric(true) is the same as inverse_of(Predicate), i.e., creating a predicate that is the inverse of itself.

transitive(+Boolean)

Sets the transitive property.

inverse_of(+Predicate2)

Define Predicate as the inverse of Predicate2. An inverse relation is deleted using inverse_of([]).

The transitive property is currently not used. The symmetric and inverse_of properties are considered by rdf_has/3,4 and rdf_reachable/3.

To be done

Maintain these properties based on OWL triples.

rdf_predicate_property(?Predicate, ?Property)

Query properties of a defined predicate. Currently defined properties are given below.

symmetric(Bool)

True if the predicate is defined to be symetric. I.e., {A} P {B} implies {B} P {A}. Setting symmetric is equivalent to inverse_of(Self).

inverse_of(Inverse)

True if this predicate is the inverse of Inverse. This property is used by rdf_has/3, rdf_has/4, rdf_reachable/3 and rdf_reachable/5.

transitive(Bool)

True if this predicate is transitive. This predicate is currently not used. It might be used to make rdf_has/3 imply rdf_reachable/3 for transitive predicates.

triples(Triples)

Unify Triples with the number of existing triples using this predicate as second argument. Reporting the number of triples is intended to support query optimization.

rdf_subject_branch_factor(-Float)

Unify Float with the average number of triples associated with each unique value for the subject-side of this relation. If there are no triples the value 0.0 is returned. This value is cached with the predicate and recomputed only after substantial changes to the triple set associated to this relation. This property is intended for path optimalisation when solving conjunctions of rdf/3 goals.

rdf_object_branch_factor(-Float)

Unify Float with the average number of triples associated with each unique value for the object-side of this relation. In addition to the comments with the rdf_subject_branch_factor property, uniqueness of the object value is computed from the hash key rather than the actual values.

rdfs_subject_branch_factor(-Float)

Same as rdf_subject_branch_factor, but also considering triples of‘subPropertyOf’this relation. See also rdf_has/3.

rdfs_object_branch_factor(-Float)

Same as rdf_object_branch_factor, but also considering triples of‘subPropertyOf’this relation. See also rdf_has/3.

See also

rdf_set_predicate/2.