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1 /* Part of DML (Digital Music Laboratory)
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2 Copyright 2014-2015 Samer Abdallah, University of London
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3
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4 This program is free software; you can redistribute it and/or
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5 modify it under the terms of the GNU General Public License
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6 as published by the Free Software Foundation; either version 2
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7 of the License, or (at your option) any later version.
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8
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9 This program is distributed in the hope that it will be useful,
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10 but WITHOUT ANY WARRANTY; without even the implied warranty of
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11 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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12 GNU General Public License for more details.
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13
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14 You should have received a copy of the GNU General Public
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15 License along with this library; if not, write to the Free Software
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16 Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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17 */
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18
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19 :- module(uripattern, [
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20 simplify/2
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21 , pattern_uri/2
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22 ]).
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23
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24 :- use_module(library(semweb/rdf_db), [ rdf_global_id/2 ]).
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25
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26 :- multifile uripattern:def/2.
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27
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28 %% uri_constraint(+P:uripattern,?X:uri) is nondet.
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29 % Logical predicate implemented using delayed goals.
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30 pattern_uri(A,B) :- must_be(nonvar,A), resource(A,B).
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31
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32 resource(P:A,PB) :- !, rdf_global_id(P:'',Q), plain(Q+A,PB).
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33 resource(A,B) :- plain(A,B).
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34
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35 plain(\(M),B) :- def(M,A), (var(A) -> true; plain(A,B)).
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36 plain(A1/A2,B) :- plain(A1+'/'+A2,B).
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37 plain(num(N),B) :- when((nonvar(N);nonvar(B)), atom_number1(B,N)).
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38 plain(enc(A),B) :- when((nonvar(A);nonvar(B)), www_form_encode1(A,B)).
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39 plain(atm(A),A).
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40 plain(A1+A2,B) :-
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41 freeze(A1,plain(A1,B1)),
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42 freeze(A2,plain(A2,B2)),
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43 when((ground(B1),ground(B2);ground(B)), atom_concat1(B1,B2,B)).
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44 plain(A,A) :- atom(A).
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45
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46 %% simplify(+P1:uri_pattern, -P2:uri_pattern) is nondet.
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47 % Non-deterministic maximal reduction of URI pattern.
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48 simplify(E1,E3) :-
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49 reduce(E1,E2) *-> simplify(E2,E3); E1=E3.
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50
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51 % simplify resource if possible, fails otherwise
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52 % The pattern must be nonvar.
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53 reduce(A,B) :- must_be(nonvar,A), reduce1(A,B).
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54
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55 reduce1(num(N),A) :- number(N), atom_number(A,N).
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56 reduce1(atm(A),A) :- atomic(A).
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57 reduce1(\(A),B) :- nonvar(A), def(A,B).
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58 reduce1(enc(A),B) :- atomic(A), www_form_encode(A,B).
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59 reduce1(P:A,Q+A) :- rdf_global_id(P:'',Q).
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60 reduce1(A/B,A+'/'+B).
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61 reduce1(A+B,A1+B) :- reduce(A,A1).
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62 reduce1(A+B,A+B1) :- reduce(B,B1). % nb to get past these, A and B must be nonvar
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63 reduce1(A+B,AB) :- atom(A), atom(B), atom_concat(A,B,AB).
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64 reduce1((A+B)+C,A+BC) :- reduce1(B+C,BC).
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65 reduce1(A+(B+C),AB+C) :- reduce1(A+B,AB).
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66
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67 % ---------- support predicates ---------
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68
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69 atom_number1(Atom,Number) :-
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70 (nonvar(Number) -> number(Number); true),
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71 atom_number(Atom,Number).
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72
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73 www_form_encode1(Atom,Encoded) :-
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74 (nonvar(Encoded) -> atomic(Encoded); true),
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75 www_form_encode(Atom,Encoded).
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76
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77 atom_concat1(A,B,AB) :-
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78 (nonvar(AB) -> atomic(AB); true),
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79 atom_concat(A,B,AB).
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80
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