Graph
- 
 Clean up complicated layer extractionThu, 23 Feb 2017 19:36:45 +0000, by Steve Losh
 - 
 Fix syntaxThu, 23 Feb 2017 19:14:30 +0000, by Steve Losh
 - 
 Tweak negative term representationThu, 23 Feb 2017 17:43:45 +0000, by Steve Losh
 - 
 Add percept filteringFri, 17 Feb 2017 11:52:25 +0000, by Steve Losh
 - 
 Fix universe matchingMon, 13 Feb 2017 17:54:31 +0000, by Steve Losh
 - 
 Build percept ZDDsTue, 07 Feb 2017 12:29:12 +0000, by Steve Losh