SaaĊĦha  - thanks much, these comments are very useful.

> 001 - I consider that "year zero" should be clarified (maybe with an
> external link) for readers not acquainted with this concept.

After all the debate and controversy over BC, BCE, AD, etc. it has seemed that everyone is happy with the resolution that the spec simply ignore the concept altogether and assume strictly numerical years, positive, negative, and zero. The discussion of whether there is or is not a year zero usually does not occur without an associated discussion of BC/AD years and I am very much opposed to re-introducing that. 

However at the risk of re-opening the discussion, I have added the note "This specification assumes astrononical numbering, which includes the year zero."

But this does raise the issue of the default calendar, since year zero is not defined in the Gregorian calendar.

So, in addition, in 207, where it previously said 
          "'gregorian' is the only value defined, and it is the default when not present."
I have changed that to 
          "'gregorian' is the only value defined."

It would be good if we could say that the default is "astronomical" however since the calendar vocabulary contains only the term "Gregorian" I don't see that we can do this, and we probably need to keep the default unstated. 

> 101 - "close to correct" A reader may wonder how close we mean.
I've added the note:
('Close to correct' is not well-defined but is intended to mean "close enough, for the application".)

> 102 - Here, I'm reminded of the following quotation from an e-mail:
> > Thus 196u means: [...] "I hope to fill in the blanks".
> This quote (although informal) could be quite illuminating for readers
> not acquainted to what we mean.

Ok, I've changed:
       .... (this part of) the date has not been assigned, .... 
       .... (this part of) the date has not (yet) been assigned (it might be assigned in the future), ....

> 201 - The word "portion" would need to be clarified. Readers may wonder
> about constructs such as:
> 2004-(06-11)?
> 2004?-06-(11)~
> (2004-(06)~)?
> 2004-04-(1)?1
> In other words, I consider there is a need for clarifications about
> nested parentheses and the number of digits and dashes they may contain.
I have added the first three of your examples above. I did not add the third.

Instead, I added:

" '?' and '~' apply to a year, month, day, year-month, month-day, or year-month-day. They may not be applied to imcomplete parts of any of these, thus for example 2004-04-(1)?1 is not valid. "

And I added the note:

"Parentheses may be nested arbitrarily."

> 202 - We could clarify the concept of "consecutive digits". What about
> 186u-u2-05
> for example? Are these two digits to be considered consecutive?

I changed:

"As in level 1, the character 'u' is used in place of a single digit and means that the value of that digit is unspecified. It may be used twice consecutively, to replace two consecutive digits, etc., to mean that the values of those digits are unspecified."


"The character 'u' is used in place of one or more digits to means that the value of those digits are unspecified."

I don't see any need to mention consecutive digits. 

> 203 - A clarification is needed about constructs such as:
> [1667, 1760-12]
> 204 - If a book is published both in 1960 and in december 1961
> (according to what is printed in the book), is it OK to write:
> {1960, 1961-12}

I've added these two examples, as I can see no reason to exclude them.

> 205 - A reader may wonder why the following is not allowed:
> 2004-06-uu/2004-07-03
> when we mean that an event began on an unspecified day in june 2004.

I've added this.

> 207 - I wonder about the usefulness of this feature, if the only
> allowed value also is default.

Well now there is no default.  As far as its usefulness - there really isn't any claim that it is readily useful, it is a placeholder for the future.

> 209 - The datatype of the Season Qualifier is not specified. I remember
> that we wrote it would be "xs:string", but xs:string allow (right)
> parentheses and otherwise parentheses that do not need to be paired,
> which may lead to problems when parsing. We could write "xs:string
> without parentheses". I think I would prefer the datatype xs:anyURI
> with the constrain that any right parenthesis would be escaped as '%29'
> (as usual in such contexts). Using anyURI would ease language
> independent comparisons. We could qualify a season such as:
> 2001-21^(
> We could also suggest a number of adequate URIs, making clear that
> users may use any URIs they wish.

We've had this discussion.  I believe the conclusion was that since we have no idea what this parameter will look like when it is further developed - if it ever is - it is premature to try to work out these sort of details.

Thanks again. --Ray