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   Re: [xml-dev] RE: Schema vs Schema-free (was: RE: [xml-dev] XML Binary C

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- Bob Wyman wrote:

> Perhaps what is required here is the definition of a new facet
> for at least one of these types that would flag the trailing zeros as
> signficant.

You can use a pattern facet on a float, double, or decimal in the same way
you do on a string to enforce this sort of constraint.

- Rich Salz wrote:

> This is wrong.  You *can't* express it as a schema numeric type because
> the document creator must have freedom to specify the number of trailing
> zero's, not the schema.

Where is this specified?


Ed Day
Objective Systems, Inc.

----- Original Message -----
From: "Bob Wyman" <bob@wyman.us>
To: "'Rich Salz'" <rsalz@datapower.com>
Cc: "'Elliotte Rusty Harold'" <elharo@metalab.unc.edu>; "'xml-dev'"
Sent: Wednesday, April 14, 2004 1:03 PM
Subject: RE: [xml-dev] RE: Schema vs Schema-free (was: RE: [xml-dev] XML
Binary Characterization WG public list availabl)

> Rich Salz wrote:
> > Parts of X.fws concern me -- I am thinking of the
> > round-trip from XML for something like <error-rate>.500
> > </error-rate> going to a local number, out via
> > ASN.1/DER as an IEEE float, and back.  Along the way
> > it's all too likely to end up as .5, which will
> > break my digital signature -- and quite rightly,
> > since trailing zero's are semantically significant.
> I must admit that I get a little miffed whenever this kind of
> objection arises. Certainly, there is a real problem being described,
> however, it *isn't* a problem with X.fws or any of the schema-based
> alternatives to XML. Rather, the problem is that the schemas are
> underspecified. If, as you say, trailing zero's are significant, then
> that information should be expressed in the schema. If it was
> expressed in the schema, then any schema based alternative should
> honor the schema and pass along the tailing (or leading) zeros.
> This "problem" that some people attribute to X.fws and similar
> systems is really a problem with XML Schema, RelaxNg, etc. The fact
> that it becomes more obvious when you have a system like X.fws that
> relies on schema's being accurate doesn't change the fact that the
> problem exists even without using something like X.fws. For instance,
> if I (as a coder) see an XML Schema that tells me something is a
> "Float", "Decimal" or "Double", then no one should be surprised if I
> read the XML Schema specification and treat the data as defined there.
> Thus, for doubles, leading and trailing zeros are prohibited. For
> Decimal and Float, leading and tailing zeros are optional but are not
> defined to have meaning if present.
> Perhaps what is required here is the definition of a new facet
> for at least one of these types that would flag the trailing zeros as
> signficant.
> Of course, an alternative is to simply define the type of a
> field to be a string and then constrain it to contain only numeric
> values or some number-like pattern. If this is done, then none of the
> schema-based processors will do anything other than pass the data
> through as it is found in the record.
> In summary: The problem here isn't X.fws, ASN.1, etc... -- the
> problem, if any, is that the Schema language isn't expressive enough
> or that people are using the wrong data types in their schemas. If
> X.fws is used with properly defined, expressive schemas, these
> problems will not arise.
> bob wyman
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