> Since permissions are an on-going
> thing they are clearly defined by an
> interval (many of a series of incremental
> dates) rather than a single point
> (date) within a continuum. "publication
> dates of journals or other serially
> issued resources" that are still being
> published--- and to which no plans
> have been expressed to cease
> publication--- are clearly defined too by
> "open ended" intervals.
OK! We need open-ended intervals. In the light of the examples above, an
attendant question is immediately rising: Should open-ended intervals
(always) contain only ONE date?
Let's assume that journal J was first published in 2003 and is still
published as of today. We can encode that as an open-ended interval
begining in 2003, but then, the information "as of today" would not be
recorded there (read below). The concept of "today" is varying with time -
every day. At a later date, someone reading such a record containing the
open-ended interval may wonder when this information was recorded and if
such information is not available, this person will not be given more
information than "journal J was first published in 2003". The open-ended
interval would loose accuracy and be reduced to a (semantically)
non-interval "date of first publication".
On the other hand, if we choose to encode open-ended intervals with TWO
dates, we could express something like: "Journal J was first published in
2003 and was still regularly published as of 2011". Such an encoding would
make it possible to preserve the "as of date D" information which could be
useful to future readers of the record. The interval nature of the record
would be preserved for the future and would be protected from being
reduced to a (semantically) non-interval "date of first publication".
A similar reasoning could be applied to permissions as they are expressed
in the quote above.
Information of when the whole post was last updated may not be useful
enough, since other records in the post may have been updated later.
I'm aware that the terms "record", "post" and "field" are not always used
consistently, but I assume that you understand my point.