- Switching from enum indexed to String indexed Attributes 
- Merging unassociated function into classes 
- Supporting const variants of most Graphtheory classes 
- Increased Support for error handling 
- Correction to Graph copy assign operator 
- Renaming Basic_Graph.* to just Graph.* and Graph.h to Graphtheory.h 
- Eliminating Graph Specializations as they are no longer necessary 
- Adapting Maintenance_Problem classes to support new Attribute system