On Wed, 29 Dec 2010 10:07:26 -0500
"G. Ken Holman" <gkholman@xxxxxxxxxxxxxxxxxxxx> wrote:

>  Allow me to try again, please.
>
> Consider an XML document whose content model for <a> is:  ( b, c?, d )
>
> This is a valid instance:
>
>    <a>
>      <b/>
>      <c/>
>      <d/>
>    </a>
>
> But, this is also a valid instance:
>
>    <a>
>      <b/>
>      <d/>
>    </a>
>
> So, given the second instance, I run it against two stylesheets:
>
> Stylesheet 1:
>
>    <xsl:if test="not(a/c)">I'll make an assumption about a missing
> C</xsl:if>
>
> Stylesheet 2 (with a typo in it because the user mistyped):
>
>    <xsl:if test="not(a/cc)">I'll make an assumption about a missing
> C</xsl:if>
>
> Without a schema to know that <cc> is not an acceptable element,
> there is no way to distinguish the two above if statements.  With a
> schema, the second one is clearly in error.  But without a schema, it
> does not make sense to issue an error or warning about the first
> stylesheet, because it is a bona fide test I want to perform
> regarding the absence of <c>.  Hence, it cannot make the same
> assumption about the second stylesheet, and so again cannot issue an
> error or warning.

Again you're assuming the presence of a schema?

Review that given an input XML instance only.

The lack of a trigger for the xpath provides information
that is useful IMHO.

  <xsl:if test="c">
    <newC>This is a new c: <xsl:value-of select="c"/></newC>
  </xsl:if>

  <xsl:for-each select="c">
    <newC>This is a new c: <xsl:value-of select="."/></newC>
  </xsl:for-each>

I'm not arguing that extra information may be gleaned from the Schema,

just that in many cases such a schema may not be available,
an instance being used is more usually available.

--
Contact us for world-wide XML consulting & instructor-led training
Crane Softwrights Ltd.          http://www.CraneSoftwrights.com/s/
G. Ken Holman                 mailto:gkholman@xxxxxxxxxxxxxxxxxxxx
Legal business disclaimers:  http://www.CraneSoftwrights.com/legal