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Re: Feedback on precision of Decimal type.

From: Ashok Malhotra <petsa@us.ibm.com>
Date: Mon, 8 Jan 2001 10:37:40 -0500
To: "Gordon, Charles" <CGordon@netsilicon.com>
Cc: www-xml-schema-comments@w3.org
Message-ID: <OF9C54EC2F.9BE3A3DF-ON852569CE.00558F52@pok.ibm.com>

Thank you for this note.  This is precisely the kind of usage feedback
we are looking for during the CR phase.  I'm fowarding your note to the
schema-comments mailing list.  Since the length of decimal digits is
a priority feedback issue we will probably dicuss it a next week's meeting.


All the best, Ashok


"Gordon, Charles" <CGordon@netsilicon.com> on 01/04/2001 03:51:11 PM

To:   Ashok Malhotra/Watson/IBM@IBMUS, "'Paul.V.Biron@kp.org'"
      <Paul.V.Biron@kp.org>
cc:
Subject:  Feedback on precision of Decimal type.



Dear Editors,

I am starting a project using XML schema's and have therefore been reading
your spec's.  My application is to use XML to transfer data to and from
embedded devices.  One thing that concerns me in your spec is the
requirement that the Decimal type have a precision of 18 digits.  This
implies that it is represented by a 64-bit word in memory.  There was a
note
in that section requesting feedback on that decision, so here is some from
me.

I am developing code on a ARM7 processor using the Green Hills Tool set.
This compiler does not support 64-bit integers at all, not even as longs.
I
am sure that many other tool sets for 32 and 16 bit processors will also
have this limitation.  For cost reasons, most embedded applications only
use
16 or 32 bit processors.  There are some that even use 8 bit processors.
These systems are not going to be able to support 18 digit numbers
efficiently.  Most of the compiler sets for the 16 bit processors won't
even
have built in support for them.  The tool set I'm using for the ARM7 (which
is a 32-bit processor) doesn't support 18 digit numbers (and I'm sure it's
not the only one).

I am aware that I could create my own integer type that subsets the Decimal
type and constains the range of allowable values so that it can be
represented in 32-bit words.  However, this only helps me if I am writing
the schema.  There will be many applications where an embedded device may
need to support an existing schema.  In this case, the author may have
simply used the standard XML Decimal and Integer types.  The embedded
system
will be forced to support 64-bit integers even though the compiler tools do
not.  This creates extra work for the programmer and reduces the
performance
of the application.

I suspect that 32-bit words will be adequate for most applications.  I
suggest that you make the Decimal type have a precision of 9 digits.  This
is supportable with 32-bit words.  You can define another type, Long for
example, that supports 18 digits.  This would solve the problem since most
developers would only specify a Long type if their application actually
needs it.

                              ---- Charles
Received on Monday, 8 January 2001 10:37:45 GMT

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