Compares 2 symbolic. The numeric features are read from two different Generic XML inputs.
Example: compare the SCOP Folds between two unrelated protein sets, e.g. between two genomes.

The following actions are performed:
1) All categories that occur only in one set, but not in the other are shown
2) For all categories that occur in both sets the difference is calculated
3) A p-value of a Chi-Square test is returned for each category that shows if the difference from the expectation (equal in both sets) is significant.