In my GTD system the only "characterization" of the Next Action (not task) is its context. Period.
- breed Next Actions (maintaining multiple copies - what for?);
- split and merge Next Actions (they're just atoms of work and messing with atoms can be very dangerous);
- assign different types of contexts (location contexts, tool contexts, people contexts) to Next Actions - it rather does not make sense to have the ability to orthogonally assign location="office" & tool="windsurfing board" & people="mother in law" to a particular Next Action;
- assign energy types, durations, priorities or colors to Next Actions;
- create filters to hide Next Actions (I prefer the main GTD filter: Actionable now (Next Actions and Calendar items scheduled for "now") or Non-actionable now (Someday/Maybe, Calendar items scheduled for "future", Waiting for items, Tickler items).
The only "characterization" of any Project is its Area of Focus and status: Active or Someday/Maybe.
The problem with software implementations is that they promise more than they should deliver. You always will have to ask two famous Kelly Forrister's questions:
- Whatís the value in getting this done?
- Whatís the risk if I donít?
No software should be allowed to answer them for you!