8. The computer-implemented method of claim 1 , further comprising creating at least one issues-by-case metadata file, wherein the searching of the document corpus for the set of documents discussing the starting issue, the determining of the set of normalized issues discussed by the set of documents discussing the starting issue, and the determining of the instances of co-occurrences of individual normalized issues of the set of normalized issues within individual cases of the set of documents comprises searching the at least one issues-by-case metadata file.
8. The computer-implemented method of claim 1 , further comprising creating at least one issues-by-case metadata file, wherein the searching of the document corpus for the set of documents discussing the starting issue, the determining of the set of normalized issues discussed by the set of documents discussing the starting issue, and the determining of the instances of co-occurrences of individual normalized issues of the set of normalized issues within individual cases of the set of documents comprises searching the at least one issues-by-case metadata file. 9. The computer-implemented method of claim 8 , wherein the at least one issues-by-case metadata file comprises at least one entry comprising a case identifier and one or more issue identifiers.