On Tue, Nov 19, 2013 at 9:28 PM, Jukka K. Korpela <jkorp...@cs.tut.fi> wrote: > It would be too restrictive to require that, and an reality, things don’t > work that way. For example, if the action consists of deleting something, > you just can’t repeat it next.
Well, you can. Deletion is idempotent - deleting something that has already been deleted does nothing. However, if the action a button represents is not currently applicable, the button should be disabled; pressing the button again doesn't need to be possible. In any case, I don't mean to suggest that that should be 'required', just that it is part of the concept of a button and following it where possible is likely a good idea if you want users to form correct conclusions about what things will do.
