rdf11:rdf_where/1

library
- semweb

{+Where} is semidet

rdf_where(+Where) is semidet

Formulate constraints on RDF terms, notably literals. These are intended to be used as illustrated below. RDF constraints are pure: they may be placed before, after or inside a graph pattern and, provided the code contains no commit operations (!, ->), the semantics of the goal remains the same. Preferably, constraints are placed before the graph pattern as they often help the RDF database to exploit its literal indexes. In the example below, the database can choose between using the subject and/or predicate hash or the ordered literal table.

    { Date >= "2000-01-01"^^xsd:date },
    rdf(S, P, Date)

The following constraints are currently defined:

>,>=,==,=<,<: The comparison operators are defined between numbers (of any recognised type), typed literals of the same type and langStrings of the same language.
prefix(String, Pattern)
substring(String, Pattern)
word(String, Pattern)
like(String, Pattern)
icase(String, Pattern): Text matching operators that act on both typed literals and langStrings.
lang_matches(Term, Pattern): Demands a full RDF term (Text@Lang) or a plain Lang term to match the language pattern Pattern.

The predicates rdf_where/1 and {}/1 are identical. The rdf_where/1 variant is provided to avoid ambiguity in applications where {}/1 is used for other purposes. Note that it is also possible to write rdf11:{...}.