1/* Part of sparkle 2 Copyright 2014-2015 Samer Abdallah (UCL) 3 4 This program is free software; you can redistribute it and/or 5 modify it under the terms of the GNU Lesser General Public License 6 as published by the Free Software Foundation; either version 2 7 of the License, or (at your option) any later version. 8 9 This program is distributed in the hope that it will be useful, 10 but WITHOUT ANY WARRANTY; without even the implied warranty of 11 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 12 GNU Lesser General Public License for more details. 13 14 You should have received a copy of the GNU Lesser General Public 15 License along with this library; if not, write to the Free Software 16 Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA 17*/ 18 19:- module(sparql_dcg,[ 20 select//3 21 , construct//3 22 , describe//1 23 , describe//2 24 , ask//1 25 ]).

A simple DCG for generating a subset of SPARQL

sparql_goal ---> (sparql_goal, sparql_goal) % conjunction
               ; (sparql_goal; sparql_goal) % disjunction
               ; rdf(resource,resource,object)
               ; filter(cond)
               .

resource :< object. % any resource is an object

literal(+literal)   :: object.  % any ground literal is an object
atomic              :< literal. % any atomic can be a plain literal
lang(atom,atom)     :: literal. % literal with language
type(resource,atom) :: literal. % typed literal

object   :< expr. % any object is an expr
number   :< expr. % Prolog numerical values can also be expressions

condition ---> (cond , cond)
             ; (cond ; cond)
             ; \+ cond
             ; expr == expr
             ; expr \= expr
             ; expr >= expr
             ; expr =< expr
             ; expr < expr
             ; expr > expr
             ; between(expr,expr,expr)
             ; in(object,list(object))
             ; regex(pattern,value)
             ; bound(object)
             ; blank(resource)
             ; uri(object)
             ; literal(object)
             .

expr ---> expr + expr
        ; expr - expr
        ; expr * expr
        ; expr / expr
        ; +expr
        ; -expr
        ; str(expr)
        ; lang(expr)
        ; datatype(expr)
        .

var ---> '$VAR'(integer)
       ; '@'        % anonymous blank node
       ; '@'(atom)  % nonymous blank node
       .

var :< resource
var :< literal

Samer Abdallah, Dept. of Computer Science, UCL (2014) /

88%:- use_module(library(semweb/rdf_db), [rdf_global_object/2, rdf_global_id/2]). 89:- use_module(library(semweb/rdf11)). 90:- use_module(library(dcg_core)). 91:- use_module(library(dcg_codes)). 92 93:- set_prolog_flag(double_quotes, codes).

100select(_Vars,Goal,Options) --> 101 { 102 ( Goal=aggregate_group(_,_,_,_) 103 ; Goal=aggregate_group(_,_,_,_,_) 104 ; Goal=aggregate(_,_,_)) 105 }, 106 !, 107 % TODO 108 if_option(distinct(Distinct), if(Distinct=true, " "),Options,O1), 109 goal(Goal), 110 if_option(order_by(OB), (" ORDER BY ", expr(OB)), O1,O2), 111 if_option(limit(Limit), (" LIMIT ", at(Limit)), O2,O3), 112 if_option(offset(Offs), (" OFFSET ", at(Offs)), O3,O4), 113 {check_remaining_options(O4)}. 114 115select(Vars,Goal,Options) --> 116 "SELECT ", 117 if_option(distinct(Distinct), if(Distinct=true, " DISTINCT "),Options,O1), 118 seqmap_with_sep(" ",expr,Vars), " ", 119 where(Goal), 120 if_option(order_by(OB), (" ORDER BY ", expr(OB)), O1,O2), 121 if_option(limit(Limit), (" LIMIT ", at(Limit)), O2,O3), 122 if_option(offset(Offs), (" OFFSET ", at(Offs)), O3,O4), 123 {check_remaining_options(O4)}. 124 125construct(Head,Goal,Options) --> 126 {O1=Options}, 127 "CONSTRUCT ", brace(goal(Head)), " ", 128 where(Goal), 129 if_option(order_by(OB), (" ORDER BY ", expr(OB)), O1,O2), 130 if_option(limit(Limit), (" LIMIT ", at(Limit)), O2,O3), 131 if_option(offset(Offs), (" OFFSET ", at(Offs)), O3,O4), 132 {check_remaining_options(O4)}. 133 134check_remaining_options([]) :- !. 135check_remaining_options([Opt|Opts]) :- ignore_option(Opt), !, check_remaining_options(Opts). 136check_remaining_options(Opts) :- throw(unrecognised_options(Opts)). 137 138ignore_option(rule(_)). 139 140edgeprops([]) --> "". 141edgeprops([EP]) --> 142 !, 143 edgeprop(EP). 144edgeprops([EP|EPs]) --> 145 edgeprop(EP), 146 " ; ", 147 edgeprops(EPs). 148 149edgeprop(P=O) --> 150 { rdf_global_object(O,OO) }, 151 property(P), " ", 152 object(OO). 153 154 155 156if_option(Opt,Phrase,O1,O2) --> 157 ( {select_option(Opt,O1,O2)} -> call_dcg(Phrase); {O2=O1}).

178% simplify/normalize 179goal((G,true)) --> !, goal(G). 180goal((true,G)) --> !, goal(G). 181 182 183goal(G1;G2) --> brace(goal(G1)), " UNION ", brace(goal(G2)). 184goal(\+G) --> "FILTER NOT EXISTS ", brace(goal(G)). %NB consider MINUS { ... } also 185goal((G1,G2)) --> goal(G1), " . ", goal(G2). 186goal(conj(GS)) --> seqmap_with_sep(" , ",goal,GS). 187goal(optional(G)) --> "OPTIONAL ", brace(goal(G)). 188goal(exists(G)) --> "FILTER(EXISTS ", brace(goal(G)),")". 189 190goal(service(S,G)) --> "SERVICE ",{(sparql_endpoint_url(S,URL)->true;URL=S)}, resource(URL)," ",brace(goal(G)). 191 192goal(rdf_path(S,P,O,G)) --> goal(rdf(S,P,O,G)). 193goal(rdf_path(S,P,O)) --> goal(rdf(S,P,O)). 194 195 196goal(rdf(S,P,O)) --> 197 { rdf_global_object(O,OO) }, 198 resource(S), " ", 199 property(P), " ", 200 object(OO). 201 202 203goal(rdf(S,P,O,G)) --> "GRAPH ", resource(G), " ", brace(goal(rdf(S,P,O))). 204 205% RDF*. See https://github.com/blazegraph/database/wiki/Reification_Done_Right 206goal(rdfstar(S,P,O,EdgeProps)) --> 207 { rdf_global_object(O,OO) }, 208 "<<", 209 resource(S), " ", 210 property(P), " ", 211 object(OO), 212 ">> ", 213 edgeprops(EdgeProps). 214 215 216% this does not work on many triplestores 217% https://stackoverflow.com/questions/32274562/what-is-the-sparql-query-to-get-the-name-of-all-graphs-existing-in-my-triplestor 218goal(rdf_graph(G)) --> "GRAPH ", resource(G), " {}". 219 220goal(rdf_graph_goals(G,Goals)) --> "GRAPH ", resource(G), " ", brace(goal(Goals)). 221 222goal(rdf_predicate(P)) --> "SELECT DISTINCT ", expr(P), " ", where(rdf(_,P,_)). 223 224goal(aggregate(Expr,G,Result)) --> "SELECT (", expr(Expr), " AS ", variable(Result), ") ", where(G). 225goal(aggregate_group(Expr, GroupVars, G, Result)) --> 226 "SELECT (", 227 expr(Expr), " AS ", variable(Result),") ", 228 seqmap_with_sep(" ",expr,GroupVars), 229 " ", 230 where(G), 231 " GROUP BY ", seqmap_with_sep(" ",expr,GroupVars). 232goal(aggregate_group(Expr, GroupVars, G, Having, Result)) --> 233 "SELECT (", 234 expr(Expr), " AS ", variable(Result),") ", 235 seqmap_with_sep(" ",head_expr,GroupVars), 236 " ", 237 where(G), 238 " GROUP BY ", seqmap_with_sep(" ",head_expr_val,GroupVars), 239 " HAVING ", cond(Having). 240 241 242 243goal(is(V,Expr)) --> goal(bind(Expr,V)). 244goal(bind(Expr,V)) --> "BIND( ", expr(Expr), " AS ", variable(V), " )". 245goal(filter(Cond)) --> "FILTER ", cond(Cond). 246 247% support for rdf_where/1 in semweb/rdf11 248goal({Cond}) --> "FILTER ", cond(Cond). 249goal(rdf_where(Cond)) --> "FILTER ", cond(Cond). 250 251goal(member(Var,Vals)) --> 252 {ground(Vals)}, 253 !, 254 goal(values(Var,Vals)). 255goal(values(Var,Vals)) --> 256 {\+ is_list(Var)},!, 257 "VALUES ",expr(Var)," {", 258 seqmap_with_sep(" ",expr,Vals), " }". 259%goal(values(Var,Tuples)) --> "VALUES (", 260% {writeln(var=Var),writeln(tups=Tuples),trace,compound(Var), Var =.. [Pred|Args],Tuples}, 261% seqmap_with_sep(" ",expr,Args), ") {", 262% seqmap_with_sep(" ",tuple,Tuples), " }". 263goal(values(Vars,Tuples)) --> "VALUES (", 264 seqmap_with_sep(" ",expr,Vars), ") {", 265 seqmap_with_sep(" ",tuple,Tuples), " }". 266 267 268goal(true) --> "true" . 269 270% TODO: put this in its own section 271goal(str_before(Str, Sep, Sub)) --> goal(bind(str_before(Str, Sep), Sub)). 272goal(replace(Str, Match, Rep, V)) --> goal(bind(replace(Str, Match, Rep), V)). 273 274% allow conditions not wrapped by rdf_where/1 275goal(G) --> goal(filter(G)). 276 277% this is necessary for assigning variables in GROUP BY querie 278head_expr(is(V,Expr)) --> !, "BIND( ", expr(Expr), " AS ", variable(V), " )". 279head_expr(X) --> expr(X). 280 281head_expr_val(is(_V,Expr)) --> !, expr(Expr). 282head_expr_val(X) --> expr(X). 283 284 285tuple(Vals) --> "(", seqmap_with_sep(" ",expr,Vals), ")". 286 287 288:- op(1150,fx,p). 289p(X) --> paren(X). 290 291cond(\+C) --> p "! ", cond(C). 292cond((X,Y)) --> p cond(X), " && ", cond(Y). 293cond((X;Y)) --> p cond(X), " || ", cond(Y). 294cond(X=Y) --> p expr(X), " = ", expr(Y). 295cond(X==Y) --> p expr(X), " = ", expr(Y). 296cond(X\=Y) --> p expr(X), " != ", expr(Y). 297cond(X=<Y) --> p expr(X), " <= ", expr(Y). 298cond(X>=Y) --> p expr(X), " >= ", expr(Y). 299cond(X>Y) --> p expr(X), " > ", expr(Y). 300cond(X<Y) --> p expr(X), " < ", expr(Y). 301cond(X@<Y) --> p expr(str(X)), " < ", expr(str(Y)). 302cond(X@=<Y) --> p expr(str(X)), " <= ", expr(str(Y)). 303cond(X@>Y) --> p expr(str(X)), " > ", expr(str(Y)). 304cond(X@>=Y) --> p expr(str(X)), " >= ", expr(str(Y)). 305cond(between(L,U,X)) --> cond((L=<X,X=<U)). 306 307% 17.4.1.9 IN 308cond(in(X,Ys)) --> p expr(X), " in ", (p seqmap_with_sep(", ",expr,Ys)). 309cond(contains(X,Y)) --> p "contains(", string_literal_expr(X), ",", string_literal_expr(Y), ")". 310cond(str_starts(X,Y)) --> p "strStarts(", string_literal_expr(X), ",", string_literal_expr(Y), ")". 311cond(str_ends(X,Y)) --> p "strEnds(", string_literal_expr(X), ",", string_literal_expr(Y), ")". 312cond(regex(S,P)) --> p "regex(", expr(S), ",", quote(at(P)), ")". 313cond(regex(S,P,F)) --> p "regex(", expr(S), ",", quote(at(P)), ",", quote(at(F)), ")". 314cond(regex_str(S,P)) --> "regex(", expr(str(S)), ",", quote(at(P)), ")". 315cond(regex_str(S,P,F)) --> "regex(", expr(str(S)), ",", quote(at(P)), ",", quote(at(F)), ")". 316cond(bound(V)) --> "bound(", object(V), ")". 317 318% 17.4.2.1 isIRI 319% defined in rdf11 320cond(rdf_is_iri(V)) --> "isIRI(", object(V), ")". 321cond(is_uri(V)) --> "isURI(", object(V), ")". 322 323% 17.4.2.2 isBlank 324% defined in rdf11 325cond(rdf_bnode(V)) --> "isBLANK(", object(V), ")". 326cond(is_blank(V)) --> "isBLANK(", object(V), ")". 327cond(rdf_is_bnode(V)) --> "isBLANK(", object(V), ")". 328 329% 17.4.2.3 isLiteral 330% defined in rdf11 331cond(rdf_is_literal(V)) --> "isLITERAL(", object(V), ")". 332cond(is_literal(V)) --> "isLITERAL(", object(V), ")". 333 334% 17.4.2.4 isNumeric 335cond(number(V)) --> "isNumeric(", object(V), ")". 336 337 338% rdf_where/1 339cond(lang_matches(V,W)) --> "LANGMATCHES(", expr(lang(V)), ",", object(W), ")". 340 341cond(G) --> {throw(error(cond(G)))}. 342 343 344 345string_literal_expr(A) --> {atomic(A),atom_string(A,S)},expr(S). 346string_literal_expr(S) --> expr(S). 347 348% 17.4.1.2 IF 349expr(if(Expr,Yes,No)) --> "IF(", cond(Expr), ", ", expr(Yes), ", ", expr(No), ")". 350 351expr('*') --> "*". 352 353 354% [121] builtin call 355expr(str(V)) --> "STR(", object(V), ")". 356expr(strlang(V,L)) --> "STRLANG(", object(V), ",", object(L), ")". 357expr(lang(V)) --> "LANG(", object(V), ")". 358expr(langmatches(V,W)) --> "LANGMATCHES(", object(V), ",", object(W), ")". 359expr(datatype(V)) --> "DATATYPE(", object(V), ")". 360expr(bound(V)) --> "BOUND(", object(V), ")". 361expr(uri(V)) --> "URI(", expr(V), ")". 362expr(iri(V)) --> "IRI(", expr(V), ")". 363expr(rand) --> "RAND()" . 364expr(abs(V)) --> "ABS(", expr(V), ")". 365expr(ceil(V)) --> "CEIL(", expr(V), ")". 366expr(floor(V)) --> "FLOOR(", expr(V), ")". 367expr(round(V)) --> "ROUND(", expr(V), ")". 368 369expr(str_before(Str,Sep)) --> "strBefore(", string_literal_expr(Str), ", ", string_literal_expr(Sep), ")". 370expr(str_after(Str,Sep)) --> "strAfter(", string_literal_expr(Str), ", ", string_literal_expr(Sep), ")". 371expr(concat(A,B)) --> "concat(", string_literal_expr(A), ", ", string_literal_expr(B), ")". 372expr(strlen(V)) --> "STRLEN(", expr(V), ")". 373expr(substr(V,W)) --> "SUBSTR(", expr(V), ", ", expr(W), ")". % [123] 374expr(substr(V,W,X)) --> "SUBSTR(", expr(V), ", ", expr(W), ", ", expr(X), ")". % [123] 375expr(replace(S,P,R)) --> "replace(", string_literal_expr(S), ", ", string_literal_expr(P), ", ", string_literal_expr(R), ")". % [124] 376expr(replace(S,P,R,Z)) --> "replace(", string_literal_expr(S), ", ", string_literal_expr(P), ", ", string_literal_expr(R), 377 ", ", string_literal_expr(Z), ")". % [124] 378 379expr(ucase(A)) --> "ucase(", string_literal_expr(A), ")". 380expr(lcase(A)) --> "lcase(", string_literal_expr(A), ")". 381 382expr(lang(V)) --> "lang(", object(V), ")". 383 384% TODO more of 121 385 386expr(S) --> {string(S)},"\"", at(S), "\"". 387expr('^^'(S,T)) --> "\"", at(S), "\"^^", resource(T). 388expr('@'(S,Lang)) --> "\"", at(S), "\"@", at(Lang). 389expr(distinct(X)) --> "DISTINCT ", expr(X), " ". 390expr(quote(V)) --> quote(at(V)). 391 392% [127] Aggregate 393expr(max(X)) --> "max(", expr(X), ")". 394expr(min(X)) --> "min(", expr(X), ")". 395expr(sum(X)) --> "sum(", expr(X), ")". 396expr(count(X)) --> "COUNT(", expr(X), ")". 397expr(sample(X)) --> "SAMPLE(", expr(X), ")". 398expr(group_concat(X)) --> "GROUP_CONCAT(", expr(X), ")". 399expr(group_concat(X, S)) --> "GROUP_CONCAT(", expr(X), " ; SEPARATOR = ", expr(S), ")". 400 401expr(+X) --> p "+ ", expr(X), ")". 402expr(-X) --> p "- ", expr(X), ")". 403expr(X+Y) --> p expr(X), " + ", expr(Y). 404expr(X-Y) --> p expr(X), " - ", expr(Y). 405expr(X*Y) --> p expr(X), " * ", expr(Y). 406expr(X/Y) --> p expr(X), " / ", expr(Y). 407expr((X,Y)) --> p expr(X), " ", expr(Y). 408expr(X) --> {number(X)}, at(X). 409expr(X) --> object(X). 410 411% https://www.w3.org/TR/sparql11-query/#pp-language 412property(oneOrMore(R)) --> property(R),"+". 413property(zeroOrMore(R)) --> property(R),"*". 414property(zeroOrOne(R)) --> property(R),"?". 415property(inverse(R)) --> "^", property(R). 416property(\+R) --> "!(", property(R), ")". 417property(\R) --> "^(", property(R), ")". 418property(R1/R2) --> "(",property(R1),"/",property(R2),")". 419property(R1|R2) --> "(",property(R1),"|",property(R2),")". 420 421property(R) --> resource(R). 422 423resource(R) --> variable(R). 424resource(R) --> {rdf_global_id(R,RR)}, uri(RR). 425 426object(literal(Lit)) --> literal(Lit). 427object('^^'(Val,Type)) --> quote(wr(Val)), "^^", resource(Type). 428object('@'(Val,Lang)) --> quote(at(Val)), "@", at(Lang). 429object(S) --> {string(S)}, quote(at(S)). 430object(Resource) --> resource(Resource). 431 432% old-style literals 433literal(lang(Lang,Val)) --> quote(at(Val)), "@", at(Lang). 434literal(type(Type,Val)) --> quote(wr(Val)), "^^", resource(Type). 435literal(Lit) --> {atomic(Lit)}, quote(at(Lit)). 436 437uri(U) --> {atom(U)}, "<", at(U), ">". 438quote(P) --> "\"", escape_with(0'\\,0'",P), "\"". 439variable(v(V)) --> "?", at(V). 440variable(V) --> {var_number(V,N)}, "?v", at(N). 441variable('@'(V)) --> "_:", {atomic(V) -> N=V; var_number(V,N)}, at(N). 442variable(@) --> "[]"