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+# P2R
+
+A set of modules allowing you to export
+prolog predicates as RDF just by declaring
+mappings, and access them through a SPARQL 
+end-point.
+
+Yves Raimond (c) 2007
+Centre for Digital Music, Queen Mary, 
+University of London
+
+Samer Abdallah (c) 2010, 2014
+Department of Computer Science, UCL
+
+## Installation & running
+
+ 1. Get ClioPatria from here:
+ http://cliopatria.swi-prolog.org/home
+ and set it up as per instructions.
+
+ 2. Copy or link this p2r directory into the cpacks directory of
+ your working ClioPatria server.
+
+ 3. Register the cpack by doing  (at the Prolog prompt)
+
+		?- cpack_configure(p2r).
+
+ 4. In your code, do
+
+		:- use_module(entailment(p2r)).
+
+    Register any prefixes you need with rdf_register_prefix/2, declare any
+    macros with uripattern:def(_,_), and write your mapping rules.
+
+ 5. Use the triples:
+
+    a) Select p2r\_entailment on ClioPatria's SPARQL/SeRQL page...
+
+    b) ...or call p2r\_entailment:rdf/3 directly (not recommended)
+
+    c) ...or dump all the p2r\_entailment:rdf/3 triples into the main rdf database, using, eg
+
+			forall(p2r_entailment:rdf(A,B,C), rdf_assert(A,B,C,p2r)).
+
+	  Asserting the triples into a named graph (p2r) makes it easy
+	  to delete them all and re-import when things change.
+
+
+## Pattern language
+
+Resources URIs and literals are expressed using a pattern language.
+See the README in the lib directory.
+
+## Example mappings
+
+Suppose you have a predicate widget/3 which holds a database of
+widget identifiers, names, and weights, and another predicate 
+connectable/2 which describes which widgets can be connected
+to each other. Suppose also that the widgets are kept in a cabinet
+with pidgeon holes arranged in a matrix, and that the location of
+each widget is given by the predicate widget\_location/3.
+We could expose this as RDF using the following mappings:
+
+	:- rdf_register_prefix(eg,'http://www.example.org/').
+	uripattern:def(loc(X,Y),num(X)/num(Y)).
+
+	rdf(eg:widgets/enc(ID), rdf:type, eg:schema/'Widget') <== widget(ID,_,_).
+
+	widget(ID,Name,Weight) ==>
+		rdf(eg:widget/enc(ID), rdf:label, literal(Name)),
+		rdf(eg:widget/enc(ID), eg:weight, literal(type(xsd:double,Weight)).
+
+	rdf(eg:widget/enc(ID1), eg:connectsTo, eg:widget/enc(ID2) <= connectable(ID1,ID2).
+
+	rdf(eg:widget/enc(ID), eg:location, eg:storage/loc(X,Y)) <= 
+		widget_location(ID,X,Y).
+
+Note that URI patterns MUST be written into the rdf/3 terms in the head
+of the rule (ie, the consequent part of the implication, rather than the
+antecedent, no matter which way round the rule is written, using <== or ==>).
+Otherwise, it is your responsibilty to construct or analyse any URIs. Of course,
+you can use the uripattern module to help you do this.