After discussion on IRC, it was noted that "undefined" as this task is not significantly distinct from NULL. However, I prefer this task's "identify and exercise the mechanisms" approach, as opposed to [[Null]]'s more specific "check" approach. I'm certainly open to others' thoughts on how to effect improvement of the NULL task, make this task sufficiently distinct, or possibly deprecate that task. --[[User:Short Circuit|Michael Mol]] 03:04, 28 November 2009 (UTC)

:Tangentially, if this task is to be distinct from [[Null]] by way of being "talk about this" rather than "do this specific thing" (which is IMO an excellent split to have; cf. [[Eval]] and [[Eval in environment]], created by me), then they should use the ''same terminology''. —[[User:Kevin Reid|Kevin Reid]] 03:24, 28 November 2009 (UTC)

:It is distinct from [[Null]], at least in the context of [[Ada]] and other [strongly typed] languages where null is a legal ''defined'' value, as opposed to an illegal ''undefined'' value. I presume that some other solutions are wrong in this sense, i.e. when ''defined'' = any value from the type's domain set. In a properly typed language an object may bot have an ''undefined'' value unless something was badly wrong. --[[User:Dmitry-kazakov|Dmitry-kazakov]] 15:53, 15 July 2010 (UTC)