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1 # P2R
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2
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3 A set of modules allowing you to export
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4 prolog predicates as RDF just by declaring
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5 mappings, and access them through a SPARQL
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6 end-point.
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7
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8 Yves Raimond (c) 2007
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9 Centre for Digital Music, Queen Mary,
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10 University of London
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11
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12 Samer Abdallah (c) 2010, 2014
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13 Department of Computer Science, UCL
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14
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15 ## Installation & running
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16
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17 1. Get ClioPatria from here:
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18 http://cliopatria.swi-prolog.org/home
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19 and set it up as per instructions.
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20
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21 2. Copy or link this p2r directory into the cpacks directory of
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22 your working ClioPatria server.
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23
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24 3. Register the cpack by doing (at the Prolog prompt)
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25
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26 ?- cpack_configure(p2r).
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27
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28 4. In your code, do
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29
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30 :- use_module(entailment(p2r)).
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31
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32 Register any prefixes you need with rdf_register_prefix/2, declare any
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33 macros with uripattern:def(_,_), and write your mapping rules.
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34
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35 5. Use the triples:
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36
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37 a) Select p2r\_entailment on ClioPatria's SPARQL/SeRQL page...
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38
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39 b) ...or call p2r\_entailment:rdf/3 directly (not recommended)
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40
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41 c) ...or dump all the p2r\_entailment:rdf/3 triples into the main rdf database, using, eg
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42
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43 forall(p2r_entailment:rdf(A,B,C), rdf_assert(A,B,C,p2r)).
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44
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45 Asserting the triples into a named graph (p2r) makes it easy
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46 to delete them all and re-import when things change.
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47
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48
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49 ## Pattern language
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50
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51 Resources URIs and literals are expressed using a pattern language.
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52 See the README in the lib directory.
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53
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54 ## Example mappings
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55
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56 Suppose you have a predicate widget/3 which holds a database of
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57 widget identifiers, names, and weights, and another predicate
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58 connectable/2 which describes which widgets can be connected
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59 to each other. Suppose also that the widgets are kept in a cabinet
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60 with pidgeon holes arranged in a matrix, and that the location of
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61 each widget is given by the predicate widget\_location/3.
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62 We could expose this as RDF using the following mappings:
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63
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64 :- rdf_register_prefix(eg,'http://www.example.org/').
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65 uripattern:def(loc(X,Y),num(X)/num(Y)).
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66
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67 rdf(eg:widgets/enc(ID), rdf:type, eg:schema/'Widget') <== widget(ID,_,_).
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68
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69 widget(ID,Name,Weight) ==>
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70 rdf(eg:widget/enc(ID), rdf:label, literal(Name)),
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71 rdf(eg:widget/enc(ID), eg:weight, literal(type(xsd:double,Weight)).
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72
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73 rdf(eg:widget/enc(ID1), eg:connectsTo, eg:widget/enc(ID2) <= connectable(ID1,ID2).
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74
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75 rdf(eg:widget/enc(ID), eg:location, eg:storage/loc(X,Y)) <=
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76 widget_location(ID,X,Y).
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77
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78 Note that URI patterns MUST be written into the rdf/3 terms in the head
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79 of the rule (ie, the consequent part of the implication, rather than the
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80 antecedent, no matter which way round the rule is written, using <== or ==>).
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81 Otherwise, it is your responsibilty to construct or analyse any URIs. Of course,
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82 you can use the uripattern module to help you do this.
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