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Re: Potential new issue: PSVI considered harmful

From: Tim Bray <tbray@textuality.com>
Date: Thu, 13 Jun 2002 11:14:09 -0700
Message-ID: <3D08E0F1.2090209@textuality.com>
To: "Simon St.Laurent" <simonstl@simonstl.com>
Cc: www-tag@w3.org

Simon St.Laurent wrote:

> XQuery has taken a stab at reducing the PSVI to something manageable, 
> yes. (See [s1].)

This is exactly the problem.  I quote from 
http://www.w3.org/TR/query-datamodel/#psv

"The data model is defined in terms of the [XML Information
  Set] after XML Schema validity assessment. XML Schema validity
  assessment is the process of assessing an XML element information
  item with respect to an XML Schema and augmenting it and some or
  all of its descendants with properties that provide information
  about validity and type assignment. The result of schema validity
  assessment is an augmented Infoset, known as the Post
  Schema-Validation Infoset, or PSVI. "

It's just fine to want to use types and so on in XQuery (or any other 
work).  It's simply wrong to assert that types can exist only "after XML 
Schema validity assessment."  There is no way in the world to discover 
that some attribute value should be interpreted as a floating point 
number for purposes of range comparison, other than ascertaining whether 
the containing instance is valid?

An analogy: the PSVI is kind of like saying that the only way to 
ascertain a person's weight is to go through a complete top-to-bottom 
physical exam."   -Tim
Received on Thursday, 13 June 2002 14:12:03 UTC

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