W3C home > Mailing lists > Public > www-xml-schema-comments@w3.org > October to December 2010

[Bug 11531] precisionDecimal terminology

From: <bugzilla@jessica.w3.org>
Date: Mon, 13 Dec 2010 03:56:37 +0000
To: www-xml-schema-comments@w3.org
Message-Id: <E1PRzWf-0003YT-6C@jessica.w3.org>
http://www.w3.org/Bugs/Public/show_bug.cgi?id=11531

Dave Peterson <davep@iit.edu> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |davep@iit.edu

--- Comment #5 from Dave Peterson <davep@iit.edu> 2010-12-13 03:56:36 UTC ---
(In reply to comment #0)

> See http://lists.w3.org/Archives/Member/w3c-xml-schema-ig/2010Dec/0006.html
> (member only) for further details.

Much of Mike's IG was discussion leading up to his recommendation for changes
to the Datatypes spec.  I've added to that discussion (mostly adding, not
correcting) in
http://lists.w3.org/Archives/Member/w3c-xml-schema-ig/2010Dec/0007.html (also
member only).  In that note I said I'd make my recommendations here.  Will try
not to clutter my recommendations with a lot of discussion.  (Those who know me
know that won't be easy.)

In addition, two months after Mike accepted the task of writing up a
description of the relationship between IEEE 754 and precisionDecimal
(culminatine in the IG messages noted above), I wrote a more technical
description of that relationship and submitted it as a PDF attachment to
http://lists.w3.org/Archives/Member/w3c-xml-schema-ig/2010May/0010.html .  I'll
refer to this further on.

Mike recommended that we change the name of the arithmeticPrecision property of
precisionDecimal values to 'scale'.  I'm comfortable with this (based on
BigDecimal's use of "scale", not IEEE 754's) provided we have a note somewhere
explaining what precisionDecimal has to do with precision (in the various
generic senses, not just 754's specialized use of the word without an
adjective).

I concur that we explain the relationship between IEEE "exponent" and our
arithmeticPrecison/scale.  (Mike is wrong that our arithmeticPrecision/scale is
IEEE's "exponent - precision + 1"; IEEE describes both and calls both
"exponent".  It uses the variable "q" for ours and "e" for the other one,
stating that q = e - p + 1 .  I believe we should, in fact, explain how all our
representations of numerical values (sign, numericalValue,
arithmeticPrecision/scale) are in one-to-one correspondence with those of IEEE
(sign, significand, and exponent).

Mike recommended that we "Include in the specification a summary of the
analysis above  describing the relationship of the precisionDecimal type to the
abstract  decimal formats of IEEE."  I concur, provided we also include a
summary describing the relationship to BigDecimal.

Mike wishes to avoid ever using the words "type' or "datatype" when mentioning
IEEE "formats".  In fact, IEEE has simply used the word "format" to mean
essentially the same thing as our "datatype".  I'm quite comfortable with
always using "format" provided the equivalence of concept is noted somewhere.

Mike finally recommends that the relationship between our NaN and IEEE NaNs
(various qNaNs and sNaNs) be explained.  I concur.  I included a paragraph
(next to the last) in my May IG submission (see URL above) which can be a first
cut at such a description.

Finally, and along that line, we should complete the description of the
differences between precisionDecimal and IEEE 754 radix-10 formats by
describing the differences in allowed lexical representations.  A first cut at
such a description can also be found in the last several paragraphs of that May
submission.  Indeed, in some ways these may be the most striking differences
(other than
terminology) between our approach and that of IEEE.

[It's late at night.  Apologies if I've garbled anything in this comment.]

-- 
Configure bugmail: http://www.w3.org/Bugs/Public/userprefs.cgi?tab=email
------- You are receiving this mail because: -------
You are the QA contact for the bug.
Received on Monday, 13 December 2010 03:56:38 GMT

This archive was generated by hypermail 2.2.0+W3C-0.50 : Monday, 13 December 2010 03:56:40 GMT