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Re: possible bug in XML Schema 1.1 Part 2: Datatypes (was Re: question about lexical and value spaces)

From: Dave Peterson <davep@iit.edu>
Date: Fri, 18 Jan 2008 10:46:33 -0500
Message-Id: <a06240805c3b6792112d7@[]>
To: "Peter F. Patel-Schneider" <pfps@research.bell-labs.com>, noah_mendelsohn@us.ibm.com
Cc: mike@saxonica.com, www-xml-schema-comments@w3.org

At 4:25 AM -0500 2008-01-18, Peter F. Patel-Schneider wrote:

>  > Michael Kay writes:
>>  > There is intense debate about whether "ineffable values" (values with no
>>  > lexical representation) should be considered as being within the value
>  > > space or not.

>My understanding is that this is because facets really work in the value
>>From http://www.w3.org/TR/xmlschema-2/#facets
>	[Definition:] A facet is a single defining aspect of a value
>	space. Generally speaking, each facet characterizes a value
>	space along independent axes or dimensions.
>	[Definition:] A constraining facet is an optional property that
>	can be applied to a datatype to constrain its value space.
>	Constraining the value space c consequently constrains the
>	lexical space. Adding constraining facets to a base
>	type is described in Derivation by restriction (
>Or course there is a wrinkle in this wrt the pattern facet:
>	[Definition:] pattern is a constraint on the value space of
>	a datatype which is achieved by constraining the lexical
>	space to literals which match a specific pattern. The value of
>	pattern must be a regular expression.
>This works only because in 1.0 values must have lexical forms.

But ineffable values are only being proposed at this point for
anySimpleType (and possibly anyAtomicType), which cannot have facets
applied.  It is not intended that the pattern facet make values
without lexical representations be ineffable rather than removed
from the value space.
Dave Peterson

Received on Friday, 18 January 2008 15:46:49 UTC

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