I'm giving OmniFocus another chance after I found it didn't stick after I was a beta tester. I actually switched to Things for a while but that didn't stick either. Anyway, that's not actually what I wanted to blog about.
I want to talk about the use of hierarchy in contexts because I've just been reminded of one confusion I had during the beta. I should point out up front, this isn't really intended as a dig at OmniFocus specifically, more a general reflection on the nature of hierarchy and containment versus subsumption. Still with me?
OmniFocus supports GTD-style contexts such as @Online and @Email and also lets you group those contexts into a hierarchy so @Online and @Email can both be under a parent context @Computer.
As one might expect, the parent context subsumes its children. If you are @Online then you must also be @Computer, but you may be @Computer but not @Online (say while on a plane).
In light of this, the behaviour of OmniFocus is odd and almost the complete opposite of what one might expect (or want).
If you put an action in @Online it will appear not only when you set your current context to be @Online but also when you set your context to the more general @Computer. And if you put an action in @Computer, it will only appear if you are @Computer and not if you select the more specific @Online.
To me, this is completely backward. If I am @Online (and, by implication, therefore @Computer) then really I should have available to me @Computer actions as well as @Online actions. Similarly, if I wish to state I am @Computer (and therefore am either not @Online or am leaving whether or not I am unspecified) then I would not want to see those actions that require me specifically to be @Online.
The only conclusion one can draw is that the hierarchy of context in OmniFocus (or other similarly behaving GTD apps) is not about subsumption at all. If you make @A a parent of @B you are not in fact saying that @B implies @A or that @B is a special case of @A. If you use the hierarchy with that implication, it won't work at all. Instead, I think all you are saying is that @A is just a grouping of @B and other contexts you might, from time to time, want to look at together, and not a real context in its own right.
Of course, if you really want to model subsumption, you need a lattice, not a tree.