The predicates below form an experimental interface to provide more
reasoning inside the kernel of the rdf_db engine. Note that symmetric,
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 symmetric. 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
optimisation 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.