For some reason, even though there are tons of task management applications out there, I'm not able to find many that have the capability to manage task dependencies. That is to say, if I must do A before I can do B, B should not be presented as actionable until A has been completed. I'm also looking for the ability to have multiple dependencies (C requires both A and B), arbitrary dependency chain lengths (Z needs Y, Y needs X, etc, as many deep as required), and nested hierarchies of grouping categorization (ex. projects can have subprojects, which can have subprojects, ad infinitum).
So, I'm looking for applications that:
- Manage tasks
- Provide a framework to use as you choose to (ex. provide project/status/tag categorization that's user determined)
- Provide the ability to associate and reasonably view and manage task dependencies
- Provide multiple dependencies for a task
- Provide unlimited dependency chain lengths
- Provide unlimited categorization hierarcies
- Are technology agnostic (ie. either web based or platform independent)
I'm definitely not looking for:
- Manual hacks and tricks to manually deal with task dependencies
- Being forced to adhere to any specific methodology by the application (ie GTD)
- Project management software (far too involved and complicated)
- Trivial or toy software (has dependencies but is not 'robust' enough to use continuously as a system)
- Technology specific solutions (windows only, mac only, iOS only)
The two closest things I've found so far, which are close but not quite there:
- Omnifocus - Supposedly has dependencies, but is Mac only.
- Taskwarrior - Has dependencies, but is command-line with very limited UI options, which presents a learning curve.
Are there more/better options that I'm not able to find? I know it isn't a very difficult technical problem, and I'm having a hard time understanding why so few solutions provide it.
Note: I've accepted Emacs org-mode as the best answer to my question. However, I don't currently have time to ramp up on it, so I haven't personally vetted it. My acceptance is based on the answer entirely.