accurator/commit

Added random strategy, ranking based on number of users that annotated.

diff --git a/api/accurator.pl b/api/accurator.pl
index a6ea752..2c7c23b 100644
--- a/api/accurator.pl
+++ b/api/accurator.pl
@@ -334,7 +334,7 @@ strategy(random, Options) :-
 	reply_json_dict(Result).
 
 strategy(ranked_random, Options) :-
-    strategy_ranked_random(Result, Options),
+    strategy_user_ranked_random(Result, Options),
 	reply_json_dict(Result).
 
 strategy(expertise, Options) :-
diff --git a/lib/accurator/annotation.pl b/lib/accurator/annotation.pl
index a774f91..a07c507 100644
--- a/lib/accurator/annotation.pl
+++ b/lib/accurator/annotation.pl
@@ -2,7 +2,8 @@
 			  annotation_fields/2,
 			  annotations/3,
 			  annotations/4,
-			  number_of_annotations/2
+			  number_of_annotations/2,
+			  number_of_users/2
 		  ]).
 
 :- use_module(library(accurator/ui_elements)).
@@ -176,3 +177,14 @@ number_of_annotations(Uri, NumberOfAnnotations) :-
 		  Annotations), !,
 	length(Annotations, NumberOfAnnotations).
 number_of_annotations(_Uri, 0) :- !.
+
+%%	number_of_users(+Uri, -NumberOfUsers)
+%
+%	Get the number of users who annotated the object of the given uri.
+number_of_users(Uri, NumberOfUsers) :-
+	setof(User,
+		  (	    rdf(Annotation, oa:hasTarget, Uri),
+				rdf(Annotation, oa:annotatedBy, User)),
+		  Users), !,
+	length(Users, NumberOfUsers).
+number_of_users(_Uri, 0) :- !.
diff --git a/lib/accurator/recommendation/strategy_random.pl b/lib/accurator/recommendation/strategy_random.pl
index 65de9fc..3c7e33e 100644
--- a/lib/accurator/recommendation/strategy_random.pl
+++ b/lib/accurator/recommendation/strategy_random.pl
@@ -1,5 +1,6 @@
 :- module(strategy_random, [strategy_random/2,
 							strategy_ranked_random/2,
+							strategy_user_ranked_random/2,
 							random_from_bin/3]).
 
 :- use_module(library(accurator/accurator_user)).
@@ -41,6 +42,28 @@ assign_random(Number, SourceList, [Uri|List]) :-
     NewNumber is Number-1,
     assign_random(NewNumber, NewSourceList, List).
 
+
+%%      strategy_user_ranked_random(-Result, +Options)
+%
+%		Assign a number of objects in a random fassion, prioritysing
+%		items with low numbers of users that annotated them.
+strategy_user_ranked_random(Result, Options) :-
+	option(target(Target), Options),
+	option(number(Number), Options),
+	option(filter(Filter), Options),
+	% get list of all targets
+    findall(Uri, rdf(Uri, rdf:type, Target), SourceList),
+	filter(Filter, SourceList, FilteredList, Options),
+	maplist(number_of_users_pair, FilteredList, PairList),
+	% sort to create proper bins
+	keysort(PairList, SortedList),
+	group_pairs_by_key(SortedList, Bins),
+	results_from_bins(Bins, 0, Number, Result).
+
+number_of_users_pair(Uri, Number-Uri) :-
+	number_of_users(Uri, Number).
+
+
 %%      strategy_ranked_random(-Result, +Options)
 %
 %		Assign a number of objects in a random fassion, prioritysing