Ignore scheduled date in agenda if item is "CANCELLED"?

Question

Imaginee I set a deadline for Project A and the schedule date for task A1 and A2, now the project is cancelled (with CANCELLED todo keyword), which makes the scheduled date for A1 and A2 invalidated.

Note, I didn't remove the SCHEDULED: keywords in the sequential nodes. These information is useful if the project is activated again somehow.

I wonder what's the best way to ignore these dates (deadline and schedule) in the org-agenda?

The org buffer looks like this:

* CANCELLED Project A 
  DEADLINE: <2015-12-22 Tue>
** A1 
   SCHEDULED: <2015-12-25 Fri>
** A2 
   SCHEDULED: <2016-01-03 Sun>

This is the org-agenda buffer I have.

Answer 1

Children don't inherit the "done" state of their parents. They do inherit tags, so you can set a special tag on the parent and tell the agenda to ignore anything with that tag. In fact, org-mode provides such a tag out of the box: ARCHIVE. You can (un)set it with org-toggle-archive-tag (C-c C-x a); see the internal archiving section of the manual. Reviving the project is as simple as removing the archive tag (using C-c C-x a a second time).

If you want all CANCELLED projects to automatically be archived, you can have the tag automatically applied when the todo state changes:

(setq org-todo-state-tags-triggers
  '(("CANCELLED" ("ARCHIVE" . t)))) 

Answer 2

You can set the variables org-agenda-skip-scheduled-if-done and org-agenda-skip-deadline-if-done to t if you want your "done" TODO items to get skipped in the agenda.

Here's a link to the org manual node on deadlines and scheduling for more information..

So, for example:

(setq org-agenda-skip-scheduled-if-done t
      org-agenda-skip-deadline-if-done  t
      org-todo-keywords '((sequence "TODO" "|" "DONE" "CANCELLED")))

Answer 3

you can also put COMMENT keyword first so subtasks will not be scanned for Scheduled tag.

i refile all DONE tasks to "COMMENT Done" and these DONE Task are not shown in Agenda

• COMMENT Done
• ** DONE asdfg

Good point is that you can have bird eye view about which projects are commented, you dont have to look for ARCHIVE Tagged projects

Sorry for such a poorly formatted answer