> I apologize for the lengthy email.
Not at all! It is an excellent question. I'm afraid I don't have time
to dive into it deeply, but I can make one suggestion right off the
top of my head:
> 2) Define ranges for the year, month, day, or some combination of
> the three, for example, 1969-1970/07-08/19 -- that is, the 19th
> (and only the 19th) day of either July or August in either 1969
> or 1970.
The value= of <date> seems to me to be the place to do this. The
Guidelines say that value= should be a string representing a date in
a standard format, recommending ISO 8601 format. ISO 8601 does not
have any method for representing what you're looking for, here. (Nor
can it handle something like "the second Tuesday of every month".)
Thus I'd recommend you devise a scheme (which, to meet the Guidelines
requirement for "standard" must be well and publicly documented) for
what you want that does not conflict with the recommended scheme, ISO
8601. E.g., using an or-bar for alternation:
<date value="1969-07-19|1969-08-19|1970-07-19|1970-08-19" />
Extending this idea, one could use a comma for sequences of days.
Thus, my second Tue of the month could be written
Hmm... a little ugly. Perhaps we should allow whitespace in there?
<date value="2002-01-08, 2002-02-12, 2002-03-12,
2002-04-09, 2002-05-14, 2002-06-11,
2002-07-09, 2002-08-13, 2002-09-10,
2002-10-08, 2002-11-12, 2002-12-10,
2003-01-14, 2003-02-11, 2003-03-11,
2003-04-08, 2003-05-13, 2003-06-10,
2003-07-08, 2003-08-12, 2003-09-09,
2003-10-14, 2003-11-11, 2003-12-09" />
Much better. However, this only covers the 24 second Tuesdays of the
month in 2002 and 2003. Still need a method to say "second Tuesday of
each month" in general.
> Can anyone suggest how we can specify ranges for the day, month,
> or year portion of a date, as described earlier? The <dateRange>
> element seems to only allow two complete dates for the to= and
> from= attributes, e.g.,
Yes, I think <dateRange> is only intended for a range, not to
indicate uncertainty or alternation. The logic, I believe, was to
have a separate element so that two dates could be specified, one on
from= and the other on to=. But since there exists an international
standard notation for just this purpose (ISO 8601:2000 section 5.5)
which would fit nicely on value= of <date>, I think of <dateRange> as
completely superfluous, and hope we can get rid of it for P5.
(I have not gone so far as to point out that dates and times are the
same thing, just with different precision, and thus having both
<date> and <time> is superflous -- but I've thought it.)
> The <offset> tag therefore seems promising, but I'm not sure if it
> can (should) be used as I'd like:
No, I don't think it should be used that way. For example, if the
months in question were not July and August, but March and May, how
would you encode it? This (analagous to your xmp),
to me implies <date value="--03/--05">March through May</date>,
rather than <date value="--03|--05">either March or May</date>.
> Is a date range considered a 'single temporal expression'?
Yes, I think so. But an alternation of possible dates I'm not so sure
Of course some would point out that all this trying to find
structured controlled methods of encoding date information is really
only useful if you have something to do with it, and software to do