That seems a lot more rigid to me than how I work. I agree with @mcogilvie that if I used those criteria there would be things I must do that never got done. I use a task manager that supports hiding actions that cannot be done yet easily so that affects what goes into my GTD system.If I resume my vision :
- an action that I must do and I can do right now, if context/energy/time are ok, goes to my NA list.
- an action that I must do and I can't do right now because of date goes to :
- my calendar if I must do it on a specific date.
- my tickler system if this action goes to my NA list at this date (like a start date).
- an action that I must do and I don't want to do right now, goes to my tickler system for futur review (I guess this one is different for everyone).
- an action that I must do and I can't do right now because of other tasks goes to my project references (and when it's a standalone task ? )
- an action that I may do and I don't want to do right now, goes to my SMB list.
And my point is I only keep in my task manager things I can and plan to do now, during this this season. Mostly due to volume. I use Omnifocus and I use the review system that is built in with my own custom perspectives. When I have 2000 items to review in their system it's painfully slow and maintaining the staggered review periods in Omnifocus is terrible and frustrating. So I eliminated that friction entirely by moving all my someday/maybe items out into DEVONThink where I can review them by just reading a simple plain text note all at once not individually and only when I NEED to review that particular grouping of items. I can't easily review groups of items in Omnifocus. Only one project at a time and I found my self clicking reviewed without really reading or reviewing them because it took too long and I missed things. Separting the 2 classifications is far simpler and easier to manage.The main point is to not put into SMB list tasks that I take commitments even if I must deferred this task because of date / other task.