I think the discussion of date accessed has mixed together the following:
 
(1) The last time someone viewed the resource. (An indication of how much interest there is. If the date is a year ago, not much interest. If it's one minute ago, more interest.)
(2)  The last time that someone responsible for the resource said it was up to date.
(3)The time when this resource becomes (or became) valid. Like a train schedule. 
(4) The last time it was accessed by a specific url.
 
Now I think that Rebecca had (1) in mind, but that Bruce thought it was (2) and suggested that that was really "date valid" which we already have, to which Rebecca responded "no, date valid is (3)".  And I think that (4) is extraneous to the discussion and just adds un-necessary complexity.
 
Aside from my editorializing about (4), is my interpretation of this discussion (roughly) accurate?
 
--Ray