1/* Part of SWI-Prolog 2 3 Author: Jan Wielemaker 4 E-mail: J.Wielemaker@vu.nl 5 WWW: http://www.swi-prolog.org 6 Copyright (c) 2010-2013, University of Amsterdam 7 All rights reserved. 8 9 Redistribution and use in source and binary forms, with or without 10 modification, are permitted provided that the following conditions 11 are met: 12 13 1. Redistributions of source code must retain the above copyright 14 notice, this list of conditions and the following disclaimer. 15 16 2. Redistributions in binary form must reproduce the above copyright 17 notice, this list of conditions and the following disclaimer in 18 the documentation and/or other materials provided with the 19 distribution. 20 21 THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 22 "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 23 LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS 24 FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE 25 COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, 26 INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, 27 BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; 28 LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER 29 CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 30 LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN 31 ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 32 POSSIBILITY OF SUCH DAMAGE. 33*/ 34 35:- module(rdf_triple, 36 [ rdf_triples/2, % +Parsed, -Tripples 37 rdf_triples/3, % +Parsed, -Tripples, +Tail 38 rdf_reset_ids/0, % Reset gensym id's 39 rdf_start_file/2, % +Options, -Cleanup 40 rdf_end_file/1, % +Cleanup 41 anon_prefix/1 % Prefix for anonynmous resources 42 ]). 43:- use_module(library(gensym)). 44:- use_module(library(option)). 45:- use_module(library(uri)). 46:- use_module(rdf_parser). 47 48:- predicate_options(rdf_start_file/2, 1, 49 [ base_uri(atom), 50 blank_nodes(oneof([share,noshare])) 51 ]).
rdf.pl into a list of rdf/3
triples. The identifier of the main object created is returned
by rdf_triples/3.
Input is the `content' of the RDF element in the format as
generated by load_structure(File, Term, [dialect(xmlns)]).
rdf_triples/3 can process both individual descriptions as
well as the entire content-list of an RDF element. The first
mode is suitable when using library(sgml) in `call-back' mode.
99rdf_triples(RDF, Tripples) :- 100 rdf_triples(RDF, Tripples, []). 101 102rdf_triples([]) --> 103 !, 104 []. 105rdf_triples([H|T]) --> 106 !, 107 rdf_triples(H), 108 rdf_triples(T). 109rdf_triples(Term) --> 110 triples(Term, _).
117triples(description(Type, About, Props), Subject) --> 118 { var(About), 119 share_blank_nodes(true) 120 }, 121 !, 122 ( { shared_description(description(Type, Props), Subject) 123 } 124 -> [] 125 ; { make_id('_:Description', Id) 126 }, 127 triples(description(Type, about(Id), Props), Subject), 128 { assert_shared_description(description(Type, Props), Subject) 129 } 130 ). 131triples(description(description, IdAbout, Props), Subject) --> 132 !, 133 { description_id(IdAbout, Subject) 134 }, 135 properties(Props, Subject). 136triples(description(TypeURI, IdAbout, Props), Subject) --> 137 { description_id(IdAbout, Subject) 138 }, 139 properties([ rdf:type = TypeURI 140 | Props 141 ], Subject). 142triples(unparsed(Data), Id) --> 143 { make_id('_:Error', Id), 144 print_message(error, rdf(unparsed(Data))) 145 }, 146 []. 147 148 149 /******************************* 150 * DESCRIPTIONS * 151 *******************************/ 152 153:- thread_local 154 node_id/2, % nodeID --> ID 155 unique_id/1. % known rdf:ID 156 157rdf_reset_node_ids :- 158 retractall(node_id(_,_)), 159 retractall(unique_id(_)). 160 161description_id(Id, Id) :- 162 var(Id), 163 !, 164 make_id('_:Description', Id). 165description_id(about(Id), Id). 166description_id(id(Id), Id) :- 167 ( unique_id(Id) 168 -> print_message(error, rdf(redefined_id(Id))) 169 ; assert(unique_id(Id)) 170 ). 171description_id(each(Id), each(Id)). 172description_id(prefix(Id), prefix(Id)). 173description_id(node(NodeID), Id) :- 174 ( node_id(NodeID, Id) 175 -> true 176 ; make_id('_:Node', Id), 177 assert(node_id(NodeID, Id)) 178 ). 179 180properties(PlRDF, Subject) --> 181 properties(PlRDF, 1, [], [], Subject). 182 183properties([], _, Bag, Bag, _) --> 184 []. 185properties([H0|T0], N, Bag0, Bag, Subject) --> 186 property(H0, N, NN, Bag0, Bag1, Subject), 187 properties(T0, NN, Bag1, Bag, Subject).
201property(Pred0 = Object, N, NN, BagH, BagT, Subject) --> % inlined object 202 triples(Object, Id), 203 !, 204 { li_pred(Pred0, Pred, N, NN) 205 }, 206 statement(Subject, Pred, Id, _, BagH, BagT). 207property(Pred0 = collection(Elems), N, NN, BagH, BagT, Subject) --> 208 !, 209 { li_pred(Pred0, Pred, N, NN) 210 }, 211 statement(Subject, Pred, Object, _Id, BagH, BagT), 212 collection(Elems, Object). 213property(Pred0 = Object, N, NN, BagH, BagT, Subject) --> 214 !, 215 { li_pred(Pred0, Pred, N, NN) 216 }, 217 statement(Subject, Pred, Object, _Id, BagH, BagT). 218property(id(Id, Pred0 = Object), N, NN, BagH, BagT, Subject) --> 219 triples(Object, ObjectId), 220 !, 221 { li_pred(Pred0, Pred, N, NN) 222 }, 223 statement(Subject, Pred, ObjectId, Id, BagH, BagT). 224property(id(Id, Pred0 = collection(Elems)), N, NN, BagH, BagT, Subject) --> 225 !, 226 { li_pred(Pred0, Pred, N, NN) 227 }, 228 statement(Subject, Pred, Object, Id, BagH, BagT), 229 collection(Elems, Object). 230property(id(Id, Pred0 = Object), N, NN, BagH, BagT, Subject) --> 231 { li_pred(Pred0, Pred, N, NN) 232 }, 233 statement(Subject, Pred, Object, Id, BagH, BagT).
nonvar(Id), we reinify the
statement using the given Id.240statement(Subject, Pred, Object, Id, BagH, BagT) --> 241 rdf(Subject, Pred, Object), 242 { BagH = [Id|BagT] 243 -> statement_id(Id) 244 ; BagT = BagH 245 }, 246 ( { nonvar(Id) 247 } 248 -> rdf(Id, rdf:type, rdf:'Statement'), 249 rdf(Id, rdf:subject, Subject), 250 rdf(Id, rdf:predicate, Pred), 251 rdf(Id, rdf:object, Object) 252 ; [] 253 ). 254 255 256statement_id(Id) :- 257 nonvar(Id), 258 !. 259statement_id(Id) :- 260 make_id('_:Statement', Id).
266li_pred(rdf:li, rdf:Pred, N, NN) :- 267 !, 268 NN is N + 1, 269 atom_concat('_', N, Pred). 270li_pred(Pred, Pred, N, N).
277collection([], Nil) --> 278 { global_ref(rdf:nil, Nil) 279 }. 280collection([H|T], Id) --> 281 triples(H, HId), 282 { make_id('_:List', Id) 283 }, 284 rdf(Id, rdf:type, rdf:'List'), 285 rdf(Id, rdf:first, HId), 286 rdf(Id, rdf:rest, TId), 287 collection(T, TId). 288 289 290rdf(S0, P0, O0) --> 291 { global_ref(S0, S), 292 global_ref(P0, P), 293 global_obj(O0, O) 294 }, 295 [ rdf(S, P, O) ]. 296 297 298global_ref(In, Out) :- 299 ( nonvar(In), 300 In = NS:Local 301 -> ( NS == rdf, 302 rdf_name_space(RDF) 303 -> atom_concat(RDF, Local, Out) 304 ; atom_concat(NS, Local, Out0), 305 iri_normalized(Out0, Out) 306 ) 307 ; Out = In 308 ). 309 310global_obj(V, V) :- 311 var(V), 312 !. 313global_obj(literal(type(Local, X)), literal(type(Global, X))) :- 314 !, 315 global_ref(Local, Global). 316global_obj(literal(X), literal(X)) :- !. 317global_obj(Local, Global) :- 318 global_ref(Local, Global). 319 320 321 /******************************* 322 * SHARING * 323 *******************************/ 324 325:- thread_local 326 shared_description/3, % +Hash, +Term, -Subject 327 share_blank_nodes/1, % Boolean 328 shared_nodes/1. % counter 329 :- 331 retractall(shared_description(_,_,_)), 332 retractall(shared_nodes(_)). 333 (Term, Subject) :- 335 term_hash(Term, Hash), 336 shared_description(Hash, Term, Subject), 337 ( retract(shared_nodes(N)) 338 -> N1 is N + 1 339 ; N1 = 1 340 ), 341 assert(shared_nodes(N1)). 342 343 (Term, Subject) :- 345 term_hash(Term, Hash), 346 assert(shared_description(Hash, Term, Subject)). 347 348 349 /******************************* 350 * START/END * 351 *******************************/
357rdf_start_file(Options, Cleanup) :-
358 rdf_reset_node_ids, % play safe
359 reset_shared_descriptions,
360 set_bnode_sharing(Options, C1),
361 set_anon_prefix(Options, C2),
362 add_cleanup(C1, C2, Cleanup).368rdf_end_file(Cleanup) :- 369 rdf_reset_node_ids, 370 ( shared_nodes(N) 371 -> print_message(informational, rdf(shared_blank_nodes(N))) 372 ; true 373 ), 374 reset_shared_descriptions, 375 . 376 377set_bnode_sharing(Options, erase(Ref)) :- 378 option(blank_nodes(Share), Options, noshare), 379 ( Share == share 380 -> assert(share_blank_nodes(true), Ref), ! 381 ; Share == noshare 382 -> fail % next clause 383 ; throw(error(domain_error(share, Share), _)) 384 ). 385set_bnode_sharing(_, true). 386 387set_anon_prefix(Options, erase(Ref)) :- 388 option(base_uri(BaseURI), Options), 389 nonvar(BaseURI), 390 !, 391 ( BaseURI == [] 392 -> AnonBase = '_:' 393 ; atomic_list_concat(['_:', BaseURI, '#'], AnonBase) 394 ), 395 asserta(anon_prefix(AnonBase), Ref). 396set_anon_prefix(_, true). 397 398add_cleanup(true, X, X) :- !. 399add_cleanup(X, true, X) :- !. 400add_cleanup(X, Y, (X, Y)). 401 402 403 /******************************* 404 * UTIL * 405 *******************************/
411:- thread_local 412 anon_prefix/1. 413 414make_id(For, ID) :- 415 anon_prefix(Prefix), 416 !, 417 atom_concat(Prefix, For, Base), 418 gensym(Base, ID). 419make_id(For, ID) :- 420 gensym(For, ID). 421 422anon_base('_:Description'). 423anon_base('_:Statement'). 424anon_base('_:List'). 425anon_base('_:Node').
rdf_test.pl).433rdf_reset_ids :- 434 anon_prefix(Prefix), 435 !, 436 ( anon_base(Base), 437 atom_concat(Prefix, Base, X), 438 reset_gensym(X), 439 fail 440 ; true 441 ). 442rdf_reset_ids :- 443 ( anon_base(Base), 444 reset_gensym(Base), 445 fail 446 ; true 447 )
Create triples from intermediate representation
Convert the output of xml_to_rdf/3 from
library(rdf)into a list of triples of the format described below. The intermediate representation should be regarded a proprietary representation.Where `Subject' is
And `Predicate' is
And `Object' is