Expanded a couple of comments, bumped the gem patch level

[graph.njae.git] / lib / graph.njae / graph.rb

diff --git a/lib/graph.njae/graph.rb b/lib/graph.njae/graph.rb
index 288fc74f569481388a2f1f56ea272402b6f600b6..bdf75b231e0089ec0acbae0dfc9c2f5fb6d2ce8b 100644 (file)
--- a/lib/graph.njae/graph.rb
+++ b/lib/graph.njae/graph.rb
@@ -1,5 +1,9 @@
 require 'ostruct'
 
+require 'logger'
+$log = Logger.new(STDERR)
+$log.level = Logger::WARN
+
 # A simple graph library
 
 module GraphNjae
@@ -62,6 +66,10 @@ module GraphNjae
     end
     
     
+    # Calculates the initial similarity of each vertex in a product graph.
+    # If passed an optional block, that block is used to find the 
+    # initial similarity. If no block is given, every vertex is given
+    # an initial similarity of 1.0.
     def initial_similarity
       self.vertices.each do |v|
         if block_given?
@@ -73,42 +81,48 @@ module GraphNjae
       end
     end
     
-    # Performs similarity flooding on a graph
+    # Performs similarity flooding on a graph, as described by 
+    # Sergey Melnik, Hector Garcia-Molina, and Erhard Rahm, 
+    # "Similarity Flooding: A Versatile Graph Matching Algorithm 
+    #    and its Application to Schema Matching", Proceedings of 
+    # the 18th International Conference on Data Engineering (ICDE’02)
+    #
     # Assumes that the initial similarity has already been calculated
+    # If passed an optional block, it uses that block to update the 
+    # similarity on each iteration. If no block is passed, it uses the 
+    # default similarity updating method from the paper.
     def similarity_flood(opts = {})
       max_iterations = opts[:iterations] || 100
       max_residual = opts[:max_residual] || 0.001
       iteration = 1
       residual = max_residual + 1
       while residual > max_residual and iteration <= max_iterations
-# puts "Starting iteration #{iteration}"        
+        $log.debug { "Starting iteration #{iteration}" }
         self.vertices.each do |v|
           v.last_similarity = v.similarity
         end
         self.vertices.each do |v|
-# puts "Processing vertex #{v.name}"          
-          edge_groups = v.edges.group_by {|e| e.type }
-# puts "  Edge groups {#{edge_groups.keys.map {|t| t.to_s + ' => {' + edge_groups[t].map {|e| e.to_s}.join(', ')}.join('; ')}}"          
-          edge_groups.each do |type, edges|
-# puts "    Processing group type #{type}"
-            n = edges.length
-            edges.each do |e|
-              e.other_end(v).similarity += v.last_similarity / n
+          if block_given?
+            v.similarity = yield v
+          else
+            $log.debug { "Processing vertex #{v.name}" }
+            edge_groups = v.edges.group_by {|e| e.type }
+            $log.debug { "  Edge groups {#{edge_groups.keys.map {|t| t.to_s + ' => {' + edge_groups[t].map {|e| e.to_s}.join(', ')}.join('; ')}}" }
+            edge_groups.each do |type, edges|
+              $log.debug { "    Processing group type #{type}" }
+              n = edges.length
+              edges.each do |e|
+                e.other_end(v).similarity += v.last_similarity / n
+              end
             end
           end
         end
-#         self.vertices.each do |v|
-#           n = v.neighbours.length
-#           v.neighbours.each do |neighbour|
-#             neighbour.similarity += v.last_similarity / n
-#           end
-#         end
         max_similarity = vertices.map {|v| v.similarity}.max
         self.vertices.each do |v|
           v.similarity = v.similarity / max_similarity
         end
         residual = Math.sqrt(self.vertices.reduce(0) {|a, v| a += (v.similarity - v.last_similarity) ** 2})
-# puts "Residual = #{residual.round(3)}, sims = #{self.vertices.map {|v| v.name + " = " + v.similarity.round(2).to_s}}"
+        $log.debug { puts "Residual = #{residual.round(3)}, sims = #{self.vertices.map {|v| v.name + " = " + v.similarity.round(2).to_s}}" }
         iteration += 1
       end