[xsl] Issues with xs:error in the XPath 3.0 and XDM 3.0 Recommendations.

Subject: [xsl] Issues with xs:error in the XPath 3.0 and XDM 3.0 Recommendations.
From: Dimitre Novatchev <dnovatchev@xxxxxxxxx>
Date: Fri, 18 Apr 2014 21:26:23 -0700
 Section "2.5.1 Predefined Schema Types"  of the W3C XPath 3.0
Recommendation (http://www.w3.org/TR/xpath-30/#id-types) says :

"The schema types defined in [XQuery and XPath Data Model (XDM) 3.0]
are summarized below.

1. ....................................
2. ....................................

..............................................

6. [Definition: xs:error is a simple type with no value space, defined
in [XML Schema 1.1]. In implementations that support XML Schema 1.1,
it can be used in the 2.5.4 SequenceType Syntax to raise errors.]"

So, according to the first sentence in the citation, all the 6 types
are "defined in [XQuery and XPath Data Model (XDM) 3.0] ".

A simple search in the XQuery and XPath Data Model (XDM) 3.0 W3C
Recommendation for the string "xs:error", returns 0 results.

In the XDM 3.0 Recommendation there are three type diagrams:

  -  XPath 3.0 and XQuery 3.0 Type Hierarchy. Part1: Items

  -  XPath 3.0 and XQuery 3.0 Type Hierarchy. Part2: Simple and Complex Types

  -  XPath 3.0 and XQuery 3.0 Type Hierarchy. Part3: Atomic Types.

The type xs:error is absent in any of these charts.

This raises a number of questions:

  1. Does the XPath 3.0 type system consist of types that are defined
in XDM 3.0, or not?

  2. Is the above (cited) statement in Section "2.5.1 Predefined
Schema Types"  of the W3C XPath 3.0 Recommendation  true, that all
listed 6 types are defined in  XDM 3.0?

  3. Is actually the XPath 3.0 recommendation using type(s) that are
not defined, or even mentioned, in XDM 3.0, and if this is true, is
then another statement true from the XPath 3.0 Recommendation
          "[XQuery and XPath Data Model (XDM) 3.0] defines the data
model that underlies all XPath 3.0 expressions"    ?

  4. Where in the type hierarchy is the type xs:error located --
which, if any is its immediate base type?

  5. Section "2.5.7 xs:error" of the XPath 3.0 Recommendation
describes the xs:error type. This is different from the formal
definition of xs:error in the XML Schema 1.1 Recommendation (Section
3.16.7.3 http://www.w3.org/TR/xmlschema11-1/#xsd-error). Which of the
two definitions of xs:error (in XPath 3.0 or in XSD 1.1) is the
normative one and which is the redundant one?

  6. Section "2.5.7 xs:error" of the XPath 3.0 Recommendation states
that "A cast to xs:error raises an error or returns the empty
sequence."  In what cases is an error raised and in what cases is the
empty sequence returned?  What are examples of the two different
situations? In which document should we find the answer to this
question?

  7. Where to find a set of examples of each potential kind of use of
xs:error in an XPath expression ?



Cheers,
Dimitre Novatchev

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