hdt_open(-HDT, +File) is det

 hdt_open(-HDT, +File, +Options) is det

Open an existing HDT file and unify HDT with a handle to it. The handle is an opaque symbol that is subject to (atom) garbage collection.

File is expanded by absolute_file_name/3, with the default extension `.hdt`.

Options:

access(+Access)

How the file is accessed. One of map (map the file into memory, default) or load (load the content of the file).

indexed(+Boolean)

Whether an index is created. Default is true. Such an index is needed for partially instantiated calls to hdt_search/4. The index is maintained in a file with extension `.index` in the same directory as the HDT file. An index is not needed if you only want to extract all triples.

 hdt_search(+HDT, ?S, ?P, ?O)

True if <S,P,O> is a triple in HDT.

 hdt_header(+HDT, ?S, ?P, ?O)

True if <S,P,O> is a triple in the header of HDT.

 hdt_subject(+HDT, ?S) is nondet

 hdt_predicate(+HDT, ?P) is nondet

 hdt_object(+HDT, ?O) is nondet

 hdt_shared(+HDT, ?SO) is nondet

 hdt_node(+HDT, ?Node) is nondet

Enumerate possible values for the individual components of the triples represented in the HDT. Note that these enumarators do not enumerate blank nodes. The predicate hdt_shared/2 enumerates resources that exist in the dataset both as subject and object. If the second argument is instantiated hdt_search/4 is used to perform an indexed search and the predicates are semidet.

 hdt_suggestions(+HDT, +Base, +Role, +MaxResults, -Results:list) is det

True when Results is a list of suggestions for Base in the triple role Role. Some experimentation suggests it performs a prefix match on the internal string representation. This implies that literals are only found if the first character of Base is `"`.

Arguments:

Base	- is a string or atom
Role	- is one of subject, predicate or object

 hdt_property(+HDT, ?Property) is nondet

True if Property is a property of HTD. Defined properties are

• mapping(-Mapping)
• max_id(-ID))
• max_object_id(-ID))
• max_predicate_id(-ID))
• max_subject_id(-ID))
• objects(-Count))
• predicates(-Count))
• shared(-Count))
• subjects(-Count))
• elements(-Count))

 hdt_subject_id(+HDT, ?Subject:atom, ?Id:integer) is semidet

 hdt_predicate_id(+HDT, ?Predicate:atom, ?Id:integer) is semidet

 hdt_object_id(+HDT, ?Object:any, ?Id:integer) is semidet

True if String is mapped to Id in the given role. Fails if the requested String or Id is not known for the given role in HDT.

Arguments:

Role	- is one of subject, predicate or object

 hdt_pre_triple(+HDT, ?TripleIn, -TripleID) is det

 hdt_post_triple(+HDT, ?TripleIn, +TripleID) is det

Perform term->id and id->term translation for triples. The predicate hdt_search/4 could be defined as:

hdt_search(HDT, S, P, O) :-
    Triple   = t(S,P,O),
    TripleID = t(SID,PID,OID),
    hdt_pre_triple(HDT, Triple, TripleID),
    hdt_search_id(HDT,SID,PID,OID),
    hdt_post_triple(HDT, Triple, TripleID).

See also

- hdt_search_id/4.

 hdt_search_id(+HDT, ?S:integer, ?P:integer, ?O:integer) is nondet

True if a triple with the indicated identifiers exists.

 hdt_search_cost(HDT, ?S, ?P, ?O, -Cost:nonneg) is det

 hdt_create_from_file(+HDTFile, +RDFFile, +Options)

Create a HDT file from an RDF file. RDFFile must be in ntriples format. Options:

base_uri(+URI)

URI is used for generating the header properties (see http_header/4.

Undocumented predicates

The following predicates are exported, but not or incorrectly documented.

 hdt_open(Arg1, Arg2, Arg3)

 hdt_close(Arg1)

 hdt_predicate(Arg1, Arg2)

 hdt_shared(Arg1, Arg2)

 hdt_object(Arg1, Arg2)

 hdt_node(Arg1, Arg2)

 hdt_predicate_id(Arg1, Arg2, Arg3)

 hdt_object_id(Arg1, Arg2, Arg3)

 hdt_post_triple(Arg1, Arg2, Arg3)