I think the productivity tag may be so generic that it is not a useful sort/definition mechanism.
Looking at Wikipedia they define this as:
The term productivity software is usually used as a category of applications dedicated to helping accomplish specific jobs such as documents, presentations, spreadsheets, databases, charts and graphs, create digital paintings, electronic music, make digital movies, etcetera. Usually the most common productivity applications are, in order of importance: word processing programs, that are used to create digital or printed text documents, immediately followed by spreadsheet applications that can be used to create charts of complex iterative calculations, and databases that are used to manage large amounts of data.
This makes me think that the subordinate topics are the appropriate level of tag...i.e. word processing, presentation software, data management software etc.