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) 2010-2017, University of Amsterdam 7 VU University Amsterdam 8 All rights reserved. 9 10 Redistribution and use in source and binary forms, with or without 11 modification, are permitted provided that the following conditions 12 are met: 13 14 1. Redistributions of source code must retain the above copyright 15 notice, this list of conditions and the following disclaimer. 16 17 2. Redistributions in binary form must reproduce the above copyright 18 notice, this list of conditions and the following disclaimer in 19 the documentation and/or other materials provided with the 20 distribution. 21 22 THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 23 "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 24 LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS 25 FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE 26 COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, 27 INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, 28 BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; 29 LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER 30 CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 31 LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN 32 ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 33 POSSIBILITY OF SUCH DAMAGE. 34*/ 35 36:- module(sparql_client, 37 [ sparql_query/3, % +Query, -Row, +Options 38 sparql_set_server/1, % +Options 39 sparql_read_xml_result/2, % +Stream, -Result 40 sparql_read_json_result/2 % +Input, -Result 41 ]). 42:- use_module(library(http/http_open)). 43:- use_module(library(http/json)). 44:- use_module(library(lists)). 45:- use_module(library(rdf)). 46:- use_module(library(semweb/turtle)). 47:- use_module(library(option)).
rdf(S,P,O) for CONSTRUCT and DESCRIBE queries, row(...) for
SELECT queries and true or false for ASK queries.
Options are
SELECT query.
Remaining options are passed to http_open/3. The defaults for
Host, Port and Path can be set using sparql_set_server/1. The
initial default for port is 80 and path is /sparql/.
For example, the ClioPatria server understands the parameter
entailment. The code below queries for all triples using
_rdfs_entailment.
?- sparql_query('select * where { ?s ?p ?o }',
Row,
[ search([entailment=rdfs])
]).
116sparql_query(Query, Row, Options) :-
117 sparql_param(scheme(Scheme), Options, Options1),
118 sparql_port(Scheme, Port, Options1, Options2),
119 sparql_param(host(Host), Options2, Options3),
120 sparql_param(path(Path), Options3, Options4),
121 select_option(search(Extra), Options4, Options5, []),
122 select_option(variable_names(VarNames), Options5, Options6, _),
123 sparql_extra_headers(HTTPOptions),
124 http_open([ scheme(Scheme),
125 host(Host),
126 port(Port),
127 path(Path),
128 search([ query = Query
129 | Extra
130 ])
131 | Options6
132 ], In,
133 [ header(content_type, ContentType),
134 status_code(Status)
135 | HTTPOptions
136 ]),
137 plain_content_type(ContentType, CleanType),
138 read_reply(Status, CleanType, In, VarNames, Row).147sparql_extra_headers( 148 [ request_header('Accept' = 'application/sparql-results+xml, \c 149 application/n-triples, \c 150 application/x-turtle; q=0.9, \c 151 application/turtle; q=0.9, \c 152 text/turtle, \c 153 application/sparql-results+json, \c 154 application/rdf+xml, \c 155 text/rdf+xml; q=0.8, \c 156 */*; q=0.1'), 157 cert_verify_hook(ssl_verify) 158 ]). 159 160:- public ssl_verify/5.
166ssl_verify(_SSL,
167 _ProblemCertificate, _AllCertificates, _FirstCertificate,
168 _Error).172read_reply(200, ContentType, In, Close, Row) :- 173 !, 174 read_reply(ContentType, In, Close, Row). 175read_reply(Status, _ContentType, In, _Close, _Row) :- 176 call_cleanup(read_string(In, _, Reply), 177 close(In, [force(true)])), 178 throw(error(sparql_error(Status, Reply), _)). 179 180read_reply('application/rdf+xml', In, _, Row) :- 181 !, 182 call_cleanup(load_rdf(stream(In), RDF), close(In)), 183 member(Row, RDF). 184read_reply(MIME, In, _, Row) :- 185 turtle_media_type(MIME), 186 !, 187 call_cleanup(rdf_read_turtle(stream(In), RDF, []), close(In)), 188 member(Row, RDF). 189read_reply(MIME, In, VarNames, Row) :- 190 sparql_result_mime(MIME), 191 !, 192 call_cleanup(sparql_read_xml_result(stream(In), Result), 193 close(In)), 194 varnames(Result, VarNames), 195 xml_result(Result, Row). 196read_reply(MIME, In, VarNames, Row) :- 197 json_result_mime(MIME), 198 !, 199 call_cleanup(sparql_read_json_result(stream(In), Result), 200 close(In)), 201 ( Result = select(VarNames, Rows) 202 -> member(Row, Rows) 203 ; Result = ask(True) 204 -> Row = True, 205 VarNames = [] 206 ). 207read_reply(Type, In, _, _) :- 208 read_stream_to_codes(In, Codes), 209 string_codes(Reply, Codes), 210 close(In), 211 throw(error(domain_error(sparql_result_document, Type), 212 context(_, Reply))). 213 214turtle_media_type('application/x-turtle'). 215turtle_media_type('application/turtle'). 216turtle_media_type('application/n-triples'). 217turtle_media_type('text/rdf+n3'). 218turtle_media_type('text/turtle'). 219 220sparql_result_mime('application/sparql-results+xml'). % official 221sparql_result_mime('application/sparql-result+xml'). 222 223json_result_mime('application/sparql-results+json'). 224 225 226plain_content_type(Type, Plain) :- 227 sub_atom(Type, B, _, _, (;)), 228 !, 229 sub_string(Type, 0, B, _, Main), 230 normalize_space(atom(Plain), Main). 231plain_content_type(Type, Type). 232 233xml_result(ask(Bool), Result) :- 234 !, 235 Result = Bool. 236xml_result(select(_VarNames, Rows), Result) :- 237 member(Result, Rows). 238 239varnames(ask(_), _). 240varnames(select(VarTerm, _Rows), VarNames) :- 241 VarTerm =.. [_|VarNames]. 242 243 244 /******************************* 245 * SETTINGS * 246 *******************************/ 247 248:- dynamic 249 sparql_setting/1. 250 251sparql_setting(scheme(http)). 252sparql_setting(path('/sparql/')). 253 254sparql_param(Param, Options0, Options) :- 255 select_option(Param, Options0, Options), 256 !. 257sparql_param(Param, Options, Options) :- 258 sparql_setting(Param), 259 !. 260sparql_param(Param, Options, Options) :- 261 functor(Param, Name, _), 262 throw(error(existence_error(option, Name), _)). 263 264sparql_port(_Scheme, Port, Options0, Options) :- 265 select_option(port(Port), Options0, Options), 266 !. 267sparql_port(_Scheme, Port, Options, Options) :- 268 sparql_setting(port(Port)), 269 !. 270sparql_port(http, 80, Options, Options) :- 271 !. 272sparql_port(https, 443, Options, Options) :- 273 !.
sparql_set_server([ host(localhost),
port(8080)
path(world)
])
The default for port is 80 and path is /sparql/.
290sparql_set_server([]) :- !. 291sparql_set_server([H|T]) :- 292 !, 293 sparql_set_server(H), 294 sparql_set_server(T). 295sparql_set_server(Term) :- 296 functor(Term, Name, Arity), 297 functor(Unbound, Name, Arity), 298 retractall(sparql_setting(Unbound)), 299 assert(sparql_setting(Term)). 300 301 302 /******************************* 303 * RESULT * 304 *******************************/ 305 306ns(sparql, 'http://www.w3.org/2005/sparql-results#'). 307 308/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 309Read the SPARQL XML result format as defined in 310http://www.w3.org/TR/rdf-sparql-XMLres/, version 6 April 2006. 311- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */ 312 313 /******************************* 314 * MACRO HANDLING * 315 *******************************/ 316 317% substitute 'sparql' by the namespace defined above for better 318% readability of the remainder of the code. 319 320term_subst(V, _, _, V) :- 321 var(V), 322 !. 323term_subst(F, F, T, T) :- !. 324term_subst(C, F, T, C2) :- 325 compound(C), 326 !, 327 functor(C, Name, Arity), 328 functor(C2, Name, Arity), 329 term_subst(0, Arity, C, F, T, C2). 330term_subst(T, _, _, T). 331 332term_subst(A, A, _, _, _, _) :- !. 333term_subst(I0, Arity, C0, F, T, C) :- 334 I is I0 + 1, 335 arg(I, C0, A0), 336 term_subst(A0, F, T, A), 337 arg(I, C, A), 338 term_subst(I, Arity, C0, F, T, C). 339 340term_expansion(T0, T) :- 341 ns(sparql, NS), 342 term_subst(T0, sparql, NS, T). 343 344 345 /******************************* 346 * READING * 347 *******************************/
v(Name, ...) and Rows is a
list of row(....) containing the column values in the
same order as the variable names.true or false362:- thread_local 363 bnode_map/2. 364 365sparql_read_xml_result(Input, Result) :- 366 load_structure(Input, DOM, 367 [ dialect(xmlns), 368 space(remove) 369 ]), 370 call_cleanup(dom_to_result(DOM, Result), 371 retractall(bnode_map(_,_))). 372 373dom_to_result(DOM, Result) :- 374 ( sub_element(DOM, sparql:head, _HAtt, Content) 375 -> variables(Content, Vars) 376 ; Vars = [] 377 ), 378 ( Vars == [], 379 sub_element(DOM, sparql:boolean, _, [TrueFalse]) 380 -> Result = ask(TrueFalse) 381 ; VarTerm =.. [v|Vars], 382 Result = select(VarTerm, Rows), 383 sub_element(DOM, sparql:results, _RAtt, RContent) 384 -> rows(RContent, Vars, Rows) 385 ), 386 !. % Guarantee finalization
394variables([], []). 395variables([element(sparql:variable, Att, [])|T0], [Name|T]) :- 396 !, 397 memberchk(name=Name, Att), 398 variables(T0, T). 399variables([element(sparql:link, _, _)|T0], T) :- 400 variables(T0, T). 401 402 403rows([], _, []). 404rows([R|T0], Vars, [Row|T]) :- 405 row_values(Vars, R, Values), 406 Row =.. [row|Values], 407 rows(T0, Vars, T). 408 409row_values([], _, []). 410row_values([Var|VarT], DOM, [Value|ValueT]) :- 411 ( sub_element(DOM, sparql:binding, Att, Content), 412 memberchk(name=Var, Att) 413 -> value(Content, Value) 414 ; Value = '$null$' 415 ), 416 row_values(VarT, DOM, ValueT). 417 418value([element(sparql:literal, Att, Content)], literal(Lit)) :- 419 !, 420 lit_value(Content, Value), 421 ( memberchk(datatype=Type, Att) 422 -> Lit = type(Type, Value) 423 ; memberchk(xml:lang=Lang, Att) 424 -> Lit = lang(Lang, Value) 425 ; Lit = Value 426 ). 427value([element(sparql:uri, [], [URI])], URI) :- !. 428value([element(sparql:bnode, [], [NodeID])], URI) :- 429 !, 430 bnode(NodeID, URI). 431value([element(sparql:unbound, [], [])], '$null$'). 432 433 434lit_value([], ''). 435lit_value([Value], Value).
440sub_element(element(Name, Att, Content), Name, Att, Content). 441sub_element(element(_, _, List), Name, Att, Content) :- 442 sub_element(List, Name, Att, Content). 443sub_element([H|T], Name, Att, Content) :- 444 ( sub_element(H, Name, Att, Content) 445 ; sub_element(T, Name, Att, Content) 446 ). 447 448 449bnode(Name, URI) :- 450 bnode_map(Name, URI), 451 !. 452bnode(Name, URI) :- 453 gensym('__bnode', URI0), 454 assertz(bnode_map(Name, URI0)), 455 URI = URI0.
v(Name, ...) and Rows is a
list of row(....) containing the column values in the
same order as the variable names.true or false472sparql_read_json_result(Input, Result) :- 473 setup_call_cleanup( 474 open_input(Input, In, Close), 475 read_json_result(In, Result), 476 close_input(Close)). 477 478open_input(stream(In), In, Close) :- 479 !, 480 encoding(In, utf8, Close). 481open_input(In, In, Close) :- 482 is_stream(In), 483 !, 484 encoding(In, utf8, Close). 485open_input(File, In, close(In)) :- 486 open(File, read, In, [encoding(utf8)]). 487 488encoding(In, Encoding, Close) :- 489 stream_property(In, encoding(Old)), 490 ( Encoding == Old 491 -> Close = true 492 ; set_stream(In, encoding(Encoding)), 493 Close = set_stream(In, Encoding, Old) 494 ). 495 496close_input(close(In)) :- 497 !, 498 retractall(bnode_map(_,_)), 499 close(In). 500close_input(_) :- 501 retractall(bnode_map(_,_)). 502 503read_json_result(In, Result) :- 504 json_read(In, JSON), 505 json_to_result(JSON, Result). 506 507json_to_result(json([ head = json(Head), 508 results = json(Body) 509 ]), 510 select(Vars, Rows)) :- 511 memberchk(vars=VarList, Head), 512 Vars =.. [v|VarList], 513 memberchk(bindings=Bindings, Body), 514 !, 515 maplist(json_row(VarList), Bindings, Rows). 516json_to_result(json(JSon), ask(Boolean)) :- 517 memberchk(boolean = @(Boolean), JSon). 518 519 520json_row(Vars, json(Columns), Row) :- 521 maplist(json_cell, Vars, Columns, Values), 522 !, 523 Row =.. [row|Values]. 524json_row(Vars, json(Columns), Row) :- 525 maplist(json_cell_or_null(Columns), Vars, Values), 526 Row =.. [row|Values]. 527 528json_cell(Var, Var=json(JValue), Value) :- 529 memberchk(type=Type, JValue), 530 jvalue(Type, JValue, Value). 531 532json_cell_or_null(Columns, Var, Value) :- 533 memberchk(Var=json(JValue), Columns), 534 !, 535 memberchk(type=Type, JValue), 536 jvalue(Type, JValue, Value). 537json_cell_or_null(_, _, '$null$'). 538 539jvalue(uri, JValue, URI) :- 540 memberchk(value=URI, JValue). 541jvalue(literal, JValue, literal(Literal)) :- 542 memberchk(value=Value, JValue), 543 ( memberchk('xml:lang'=Lang, JValue) 544 -> Literal = lang(Lang, Value) 545 ; memberchk('datatype'=Type, JValue) 546 -> Literal = type(Type, Value) 547 ; Literal = Value 548 ). 549jvalue('typed-literal', JValue, literal(type(Type, Value))) :- 550 memberchk(value=Value, JValue), 551 memberchk('datatype'=Type, JValue). 552jvalue(bnode, JValue, URI) :- 553 memberchk(value=NodeID, JValue), 554 bnode(NodeID, URI)
SPARQL client library
This module provides a SPARQL client. For example:
?- sparql_query('select * where { ?x rdfs:label "Amsterdam" }', Row, [ host('dbpedia.org'), path('/sparql/')]). Row = row('http://www.ontologyportal.org/WordNet#WN30-108949737') ; false.Or, querying a local server using an
ASKquery:?- sparql_query('ask { owl:Class rdfs:label "Class" }', Row, [ host('localhost'), port(3020), path('/sparql/')]). Row = true.HTTPS servers are supported using the
scheme(https)option:?- sparql_query('select * where { ?x rdfs:label "Amsterdam"@nl }', Row, [ scheme(https), host('query.wikidata.org'), path('/sparql') ]).*/