rdfs.pl

/*  Part of SWI-Prolog

    Author:        Jan Wielemaker
    E-mail:        J.Wielemaker@vu.nl
    WWW:           http://www.swi-prolog.org
    Copyright (c)  2003-2015, University of Amsterdam
                              VU University Amsterdam
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:- module(rdfs,
          [ rdfs_subproperty_of/2,      % ?SubProperties, ?Property
            rdfs_subclass_of/2,         % ?SubClass, ?Class
            rdfs_class_property/2,      % +Class, ?Property
            rdfs_individual_of/2,       % ?Resource, ?Class

            rdfs_label/2,               % ?Resource, ?Label
            rdfs_label/3,               % ?Resource, ?Language, ?Label
            rdfs_ns_label/2,            % +Resource, -Label
            rdfs_ns_label/3,            % +Resource, ?Label, -Label

            rdfs_member/2,              % ?Object, +Set
            rdfs_list_to_prolog_list/2, % +Set, -List
            rdfs_assert_list/3,         % +List, -Resource, +DB
            rdfs_assert_list/2,         % +List, -Resource

            rdfs_find/5                 % +String, +Dom, +Props, +Method, -Subj
          ]).
:- use_module(library(semweb/rdf_prefixes),
              [ (rdf_meta)/1, op(_,_,rdf_meta)
              ]).
:- use_module(rdf_db,
              [ rdf_reachable/3, rdf_equal/2, rdf_has/3, rdf_subject/1,
                rdf_global_id/2, rdf/3, rdf_has/4, rdf_member_property/2,
                rdf_bnode/1, rdf_assert/4, rdf_match_label/3
              ]).

:- autoload(library(lists),[member/2]).

/** <module> RDFS handling

This module provides various primitives for  more high-level handling of
RDF models from an RDFS viewpoint. Note  that there exist two approaches
for languages on top of RDF:

        * Provide new predicates according to the concept of the high
          level language (used in this module)

        * Extend rdf/3 relation with triples _implied_ by the high-level
          semantics.  This approach is taken by ClioPatria.
*/

                 /*******************************
                 *          EXPANSION           *
                 *******************************/

:- rdf_meta
    rdfs_subproperty_of(r,r),
    rdfs_subclass_of(r,r),
    rdfs_class_property(r,r),
    rdfs_individual_of(r,r),
    rdfs_label(r,-),
    rdfs_label(r,?,-).


                 /*******************************
                 *      PROPERTY HIERARCHY      *
                 *******************************/

%!  rdfs_subproperty_of(+SubProperty, ?Property) is nondet.
%!  rdfs_subproperty_of(?SubProperty, +Property) is nondet.
%
%   Query the property hierarchy.

rdfs_subproperty_of(SubProperty, Property) :-
    rdf_reachable(SubProperty, rdfs:subPropertyOf, Property).


                 /*******************************
                 *        CLASS HIERARCHY       *
                 *******************************/

%!  rdfs_subclass_of(+Class, ?Super) is nondet.
%!  rdfs_subclass_of(?Class, +Super) is nondet.
%
%   Generate  sub/super  classes.  rdf_reachable/3    considers  the
%   rdfs:subPropertyOf relation as well  as   cycles.  Note  that by
%   definition all classes are  subclass   of  rdfs:Resource, a case
%   which is dealt with by the 1st and 3th clauses :-(
%
%   According to production 2.4 "rdfs:Datatype", Each instance of
%   rdfs:Datatype is a subclass of rdfs:Literal.

rdfs_subclass_of(Class, Super) :-
    rdf_equal(rdfs:'Resource', Resource),
    Super == Resource,
    !,
    rdfs_individual_of(Class, rdfs:'Class').
rdfs_subclass_of(Class, Super) :-
    rdf_reachable(Class, rdfs:subClassOf, Super).
rdfs_subclass_of(Class, Super) :-
    nonvar(Class),
    var(Super),
    \+ rdf_reachable(Class, rdfs:subClassOf, rdfs:'Resource'),
    rdfs_individual_of(Class, rdfs:'Class'),
    rdf_equal(Super, rdfs:'Resource').
rdfs_subclass_of(Class, Super) :-       % production 2.4
    (   nonvar(Class)
    ->  rdf_has(Class, rdf:type, CType),
        rdf_reachable(CType, rdfs:subClassOf, rdfs:'Datatype'),
        \+ rdf_reachable(Class, rdfs:subClassOf, rdfs:'Literal'),
        rdf_equal(Super, rdfs:'Literal')
    ;   nonvar(Super)
    ->  rdf_reachable(Super, rdfs:subClassOf, rdfs:'Literal'),
        rdfs_individual_of(Class, rdfs:'Datatype')
    ).


                 /*******************************
                 *          INDIVIDUALS         *
                 *******************************/

%!  rdfs_individual_of(+Resource, +Class) is semidet.
%!  rdfs_individual_of(+Resource, -Class) is nondet.
%!  rdfs_individual_of(-Resource, +Class) is nondet.
%
%   Generate resources belonging to a class   or  classes a resource
%   belongs to. We assume everything at the `object' end of a triple
%   is a class. A validator should confirm this property.
%
%   rdfs_individual_of(+, -) does  not  exploit   domain  and  range
%   properties, deriving that if rdf(R,  P,   _)  is  present R must
%   satisfy the domain of P (and similar for range).
%
%   There are a few hacks:
%
%           * Any resource is an individual of rdfs:Resource
%           * literal(_) is an individual of rdfs:Literal

rdfs_individual_of(Resource, Class) :-
    nonvar(Resource),
    !,
    (   nonvar(Class)
    ->  (   rdf_equal(Class, rdfs:'Resource')
        ->  true
        ;   rdfs_individual_of_r_c(Resource, Class)
        ->  true
        )
    ;   rdfs_individual_of_r_c(Resource, Class)
    ).
rdfs_individual_of(Resource, Class) :-
    nonvar(Class),
    !,
    (   rdf_equal(Class, rdfs:'Resource')
    ->  rdf_subject(Resource)
    ;   rdfs_subclass_of(SubClass, Class),
        rdf_has(Resource, rdf:type, SubClass)
    ).
rdfs_individual_of(_Resource, _Class) :-
    throw(error(instantiation_error, _)).

%!  rdfs_individual_of_r_c(+Resource, ?Class) is nondet.

rdfs_individual_of_r_c(literal(_), Class) :-
    !,
    rdfs_subclass_of(Class, rdfs:'Literal').
rdfs_individual_of_r_c(^^(_,_), Class) :-
    !,
    rdfs_subclass_of(Class, rdfs:'Literal').
rdfs_individual_of_r_c(@(_,_), Class) :-
    !,
    rdfs_subclass_of(Class, rdfs:'Literal').
rdfs_individual_of_r_c(Resource, Class) :-
    (   rdf_has(Resource, rdf:type, MyClass)
    *-> rdfs_subclass_of(MyClass, Class)
    ;   rdf_equal(Class, rdfs:'Resource')
    ).


%!  rdfs_label(+Resource, -Label).
%!  rdfs_label(-Resource, +Label).
%
%   Convert between class and label.  If the label is generated from
%   the resource the it uses both rdfs:label and its sub-properties,
%   but labels registered with rdfs:label are returned first.

rdfs_label(Resource, Label) :-
    rdfs_label(Resource, _, Label).

%!  rdfs_label(+Resource, ?Lang, -Label) is multi.
%!  rdfs_label(+Resource, ?Lang, +Label) is semidet.
%!  rdfs_label(-Resource, ?Lang, ?Label) is nondet.
%
%   Resource  has  Label  in  Lang.  If  Resource  is  nonvar  calls
%   take_label/3 which is guaranteed to succeed label.

rdfs_label(Resource, Lang, Label) :-
    nonvar(Resource),
    !,
    take_label(Resource, Lang, Label).
rdfs_label(Resource, Lang, Label) :-
    rdf_has(Resource, rdfs:label, literal(lang(Lang, Label))).

%!  rdfs_ns_label(+Resource, -Label) is multi.
%!  rdfs_ns_label(+Resource, ?Lang, -Label) is multi.
%
%   Present label with  namespace  indication.   This  predicate  is
%   intended  to  provide  meaningful  short   names  applicable  to
%   ontology maintainers.  Note that this predicate is non-deterministic
%   if the resource has multiple rdfs:label properties

rdfs_ns_label(Resource, Label) :-
    rdfs_ns_label(Resource, _, Label).

rdfs_ns_label(Resource, Lang, Label) :-
    rdfs_label(Resource, Lang, Label0),
    (   rdf_global_id(NS:_, Resource),
        Label0 \== ''
    ->  atomic_list_concat([NS, Label0], :, Label)
    ;   \+ rdf_has(Resource, rdfs:label, _)
    ->  Label = Resource
    ;   member(Sep, [#,/]),
        sub_atom(Resource, B, L, A, Sep),
        sub_atom(Resource, _, A, 0, Frag),
        \+ sub_atom(Frag, _, _, _, Sep)
    ->  Len is B+L,
        sub_atom(Resource, 0, Len, _, NS),
        atomic_list_concat([NS, Label0], :, Label)
    ;   Label = Label0
    ).


%!  take_label(+Resource, ?Lang, -Label) is multi.
%
%   Get the label to use for a  resource in the give Language. First
%   tries label_of/3.  If this fails, break the Resource over # or /
%   and if all fails, unify Label with Resource.

take_label(Resource, Lang, Label) :-
    (   label_of(Resource, Lang, Label)
    *-> true
    ;   after_char(Resource, '#', Local)
    ->  Label = Local
    ;   after_char(Resource, '/', Local)
    ->  Label = Local
    ;   Label = Resource
    ).

after_char(Atom, Char, Rest) :-
    State = last(-),
    (   sub_atom(Atom, _, _, L, Char),
        nb_setarg(1, State, L),
        fail
    ;   arg(1, State, L),
        L \== (-)
    ),
    sub_atom(Atom, _, L, 0, Rest).


%!  label_of(+Resource, ?Lang, ?Label) is nondet.
%
%   True if rdf_has(Resource, rdfs:label,   literal(Lang, Label)) is
%   true,  but  guaranteed  to  generate    rdfs:label   before  any
%   subproperty thereof.

label_of(Resource, Lang, Label) :-
    rdf(Resource, rdfs:label, literal(lang(Lang, Label))),
    nonvar(Lang).
label_of(Resource, Lang, Label) :-
    rdf_equal(rdfs:label, LabelP),
    rdf_has(Resource, LabelP, literal(lang(Lang, Label)), P),
    nonvar(Lang),
    P \== LabelP.
label_of(Resource, Lang, Label) :-
    var(Lang),
    rdf_has(Resource, rdfs:label, literal(type(xsd:string, Label))).

%!  rdfs_class_property(+Class, ?Property)
%
%   Enumerate the properties in the domain of Class.

rdfs_class_property(Class, Property) :-
    rdfs_individual_of(Property, rdf:'Property'),
    rdf_has(Property, rdfs:domain, Domain),
    rdfs_subclass_of(Class, Domain).


                 /*******************************
                 *           COLLECTIONS        *
                 *******************************/

%!  rdfs_member(?Element, +Set)
%
%   As Prolog member on sets.  Operates both on attributes parsed as
%   parseType="Collection" as well as on Bag, Set and Alt.

rdfs_member(Element, Set) :-
    rdf_has(Set, rdf:first, _),
    !,
    rdfs_collection_member(Element, Set).
rdfs_member(Element, Set) :-
    container_class(Class),
    rdfs_individual_of(Set, Class),
    !,
    (   nonvar(Element)
    ->  rdf(Set, Predicate, Element),
        rdf_member_property(Predicate, _N)
    ;   findall(N-V, rdf_nth(Set, N, V), Pairs),
        keysort(Pairs, Sorted),
        member(_-Element, Sorted)
    ).

rdf_nth(Set, N, V) :-
    rdf(Set, P, V),
    rdf_member_property(P, N).

:- rdf_meta container_class(r).

container_class(rdf:'Bag').
container_class(rdf:'Seq').
container_class(rdf:'Alt').


rdfs_collection_member(Element, Set) :-
    rdf_has(Set, rdf:first, Element).
rdfs_collection_member(Element, Set) :-
    rdf_has(Set, rdf:rest, Tail),
    !,
    rdfs_collection_member(Element, Tail).


%!  rdfs_list_to_prolog_list(+RDFSList, -PrologList)
%
%   Convert ann RDFS list (result from parseType=Collection) into a
%   Prolog list of elements.

rdfs_list_to_prolog_list(Set, []) :-
    rdf_equal(Set, rdf:nil),
    !.
rdfs_list_to_prolog_list(Set, [H|T]) :-
    rdf_has(Set, rdf:first, H),
    rdf_has(Set, rdf:rest, Tail),
    !,
    rdfs_list_to_prolog_list(Tail, T).


%!  rdfs_assert_list(+Resources, -List) is det.
%!  rdfs_assert_list(+Resources, -List, +DB) is det.
%
%   Create an RDF list from the given Resources.

rdfs_assert_list(Resources, List) :-
    rdfs_assert_list(Resources, List, user).

rdfs_assert_list([], Nil, _) :-
    rdf_equal(rdf:nil, Nil).
rdfs_assert_list([H|T], List, DB) :-
    rdfs_assert_list(T, Tail, DB),
    rdf_bnode(List),
    rdf_assert(List, rdf:rest, Tail, DB),
    rdf_assert(List, rdf:first, H, DB),
    rdf_assert(List, rdf:type, rdf:'List', DB).


                 /*******************************
                 *     SEARCH IN HIERARCHY      *
                 *******************************/

%!  rdfs_find(+String, +Domain, ?Properties, +Method, -Subject)
%
%   Search all classes below Domain for a literal property with
%   that matches String.  Method is one of
%
%           * substring
%           * word
%           * prefix
%           * exact
%
%   domain is defined by owl_satisfy from owl.pl
%
%   Note that the rdfs:label field is handled by rdfs_label/2,
%   making the URI-ref fragment name the last resort to determine
%   the label.

rdfs_find(String, Domain, Fields, Method, Subject) :-
    var(Fields),
    !,
    For =.. [Method,String],
    rdf_has(Subject, Field, literal(For, _)),
    owl_satisfies(Domain, Subject),
    Fields = [Field].               % report where we found it.
rdfs_find(String, Domain, Fields, Method, Subject) :-
    globalise_list(Fields, GlobalFields),
    For =.. [Method,String],
    member(Field, GlobalFields),
    (   Field == resource
    ->  rdf_subject(Subject),
        rdf_match_label(Method, String, Subject)
    ;   rdf_has(Subject, Field, literal(For, _))
    ),
    owl_satisfies(Domain, Subject).

owl_satisfies(Domain, _) :-
    rdf_equal(rdfs:'Resource', Domain),
    !.
                                        % Descriptions
owl_satisfies(class(Domain), Resource) :-
    !,
    (   rdf_equal(Domain, rdfs:'Resource')
    ->  true
    ;   rdfs_subclass_of(Resource, Domain)
    ).
owl_satisfies(union_of(Domains), Resource) :-
    !,
    member(Domain, Domains),
    owl_satisfies(Domain, Resource),
    !.
owl_satisfies(intersection_of(Domains), Resource) :-
    !,
    in_all_domains(Domains, Resource).
owl_satisfies(complement_of(Domain), Resource) :-
    !,
    \+ owl_satisfies(Domain, Resource).
owl_satisfies(one_of(List), Resource) :-
    !,
    memberchk(Resource, List).
                                        % Restrictions
owl_satisfies(all_values_from(Domain), Resource) :-
    (   rdf_equal(Domain, rdfs:'Resource')
    ->  true
    ;   rdfs_individual_of(Resource, Domain)
    ),
    !.
owl_satisfies(some_values_from(_Domain), _Resource) :- !.
owl_satisfies(has_value(Value), Resource) :-
    rdf_equal(Value, Resource).


in_all_domains([], _).
in_all_domains([H|T], Resource) :-
    owl_satisfies(H, Resource),
    in_all_domains(T, Resource).

globalise_list([], []) :- !.
globalise_list([H0|T0], [H|T]) :-
    !,
    globalise_list(H0, H),
    globalise_list(T0, T).
globalise_list(X, G) :-
    rdf_global_id(X, G).