Gabriel BODARD wrote:
> Final question, out of interest... how would you express:
> "17th July (definitely and precisely). Don't know which year, but almost 
> certainly mid-sixteenth century."?

Because of the imprecise formulation of 'mid-sixteenth century' as a 
period, I would encode this as:

<date when="--07-17" period="#mid16thC">17th July</date>

(-- is the W3C notation for an omitted year, there are a number of ways to 
do the same thing in ISO with @when-iso)

Elsewhere I would define what I meant by 'mid16thC' either in prose:

<p xml:id="mid16thC">Oh somewhere near the middle area of the 16th Century</p>

or more precisely:

<date xml:id="mid16thC" from="1540-01-01" to="1560-12-31">The dates we are 
using for our designation 'middle of the 16th Century'</date>

or something like that.

With respect to dates and precision, I still feel the W3C/ISO dating 
attributes have a set amount of precision inbuilt into them which is good 
for the majority of cases.  If someone wants greater precision, then they 
shouldn't be using those attributes.  Indicating which is more exact used 
to be done on dateRange with an @exact attribute, which caused lots of 
confusion.  Since dateRanges can be expressed cleanly in ISO style dates 
and thus the @*-iso attributes.  What I find more interesting is that in P5 
you can not only indicate @from and @to, but with the ISO versions of those 
attributes you can indicate a range of time from and a range of time to. So 
you can say 'from sometime in these two months' to something in this 
fortnight.  Likewise you can do this with @notBefore-iso and @notAfter-iso. 
  This can mean some quite confusing situations of imprecision can be 

It is clear what a date range means on a @from-iso/@to-iso:

<date from-iso="1540-03-17/P2M" to-iso="1560-02-14/14D"> This thing ran 
from sometime in the two months following St Patrick's Day in 1540, and 
lasted until sometime during the fortnight after Valentine's day in 

So something which runs from one date to another.  But gets slightly more 
confusion, I think, when one uses notBefore-iso and notAfter-iso to locate 
something which which is a singular date, not a date range, by means of ranges.

<date notBefore-iso="1540-03-17/P2M" notAfter-iso="1560-02-14/14D"> We 
aren't sure of the exact date of this thing, but we know it certainly was 
not before some imprecise date somewhere in the two months following St 
Patrick's Day in 1540, and certainly not after some imprecise date 
somewhere in the fortnight after Valentine's day in 1560.</date>

When one adds a @cert to this, is it both attributes that it applies to? Is 
it the notBefore/notAfter aspect or the ranges inside? What if you are 
certain of one range, but much less certain of the other?  I've always felt 
that if one truly wants to record certainty and/or precision (in anything 
other than a generalised 'high/medium/low' for the interpretation as a 
whole), then a single attribute is always bound to disappoint.  But I'm 
watching the discussion with interest.

Dr James Cummings, Oxford Text Archive, University of Oxford
James dot Cummings at oucs dot ox dot ac dot uk