Span returns all frequent sub graphs, including all sub graphs of the maximal frequent sub graph. Since the maximal frequent sub graphs are returned, any sub graphs contained therein are unnecessary....

Span returns all frequent sub graphs, including all sub graphs of the maximal frequent sub graph. Since the maximal frequent sub graphs are returned, any sub graphs contained therein are unnecessary. An example of this taken to the extreme is the single edge sub graphs that are returned. These, although possibly frequent, often give us no valuable information about the set of graphs. To solve this problem, one could simply check before returning graphs to see if they are contained within another graph that is to be returned. Another option would be to disregard smaller graphs if they are used to build larger ones.