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CR-22: Allow negative scale? WG response

From: Henry S. Thompson <ht@cogsci.ed.ac.uk>
Date: 05 Mar 2001 15:59:33 +0000
To: www-xml-schema-comments@w3.org
Cc: MFC@uk.ibm.com
Message-ID: <f5bhf18uryy.fsf@cogsci.ed.ac.uk>
[Apologies to Mike C -- retransmission to the comments list]

The W3C XML Schema Working Group has spent the last weeks and months
working through the comments received from the public on the Candidate
Recommendation (CR) of the XML Schema specification. We thank you for
the comments you made on our specification during our CR comment
period, and want to make sure you know that all comments received
during the CR comment period have been recorded in our CR issues list
( http://www.w3.org/2000/12/xmlschema-crcomments.html).

You raised the point registered as issue CR-22:

Issue Title: Allow negative scale?

You specifically said in your note [1]:

  "Currently the scale of decimal numbers is restricted to be zero or
  positive.  It is requested that this restriction be removed (that
  is, in the value of scale must be an integer, not a
  nonNegativeInteger) for the following reasons:

   "a) The current specification allows the representation of very small
      numbers (for example 1E-100) but does not permit the efficient
      representation of even moderately large numbers (for example 13
      billion, or 13E+9), even though such numbers are common in
      commerce.  Allowing positive exponents (negative scales) will
      correct the specification so both large and small numbers can be
      represented equally efficiently."

First may I note a possible misunderstanding underlying your request:
the lexical form of decimals with a positive scale does _not_ differ
from those with (implicit) 0 scale.  In other words

 <elt value="3"/>

always represents the value 3, regardless of the value of the scale
facet of the type associated with the 'value' attribute.  It follows
that the asymmetry you describe in (a) above does not exist: the
situation is worse than you thought :-).

In its discussions the WG considered quite seriously whether we should
therefore not only allow negative scale, but also interpret positive
scale in the way you evidently thought it was already interpreted.  In
the end the WG decided that on balance the ease of representation
which such a change would allow did not outweigh the substantial loss
of transparency which would result.

There is sentiment in the WG towards allowing some form of exponential 
notation for decimals in future, but it would be explicit in instances
(e.g. value="3E-10"), not implicit in type definitions.

It would be helpful to us to know whether you are satisfied with the
decision taken by the WG on this issue, or wish your dissent from the
WG's decision to be recorded for consideration by the Director of the

Thanks again for your input, and I apologise for letting this reply
slip down my stack to the point it has been unhelpfully delayed,


[1] http://lists.w3.org/Archives/Public/www-xml-schema-comments/2000OctDec/0314
  Henry S. Thompson, HCRC Language Technology Group, University of Edinburgh
          W3C Fellow 1999--2001, part-time member of W3C Team
     2 Buccleuch Place, Edinburgh EH8 9LW, SCOTLAND -- (44) 131 650-4440
	    Fax: (44) 131 650-4587, e-mail: ht@cogsci.ed.ac.uk
		     URL: http://www.ltg.ed.ac.uk/~ht/
Received on Monday, 5 March 2001 10:59:39 UTC

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