RE: Namespace undeclarations in 1.1

Thanks for the response. As so often happens, I didn't find what I was
looking for because I was looking (very carefully) in the wrong place.

Michael Kay 

> -----Original Message-----
> From: Richard Tobin [mailto:richard@inf.ed.ac.uk] 
> Sent: 11 October 2004 23:49
> To: Michael Kay; xml-names-editor@w3.org
> Subject: Re: Namespace undeclarations in 1.1
> 
> > Does the construct xmlns:p="" make p be "out of scope", so 
> any reference to
> > p is an error, or does it make p refer to the 
> non-namespace, in the same way
> > as xmlns="" makes the default prefix refer to the non-namespace?
> 
> The former.
> 
> > But what replaces this previous association?
> 
> Given:
> 
>   <foo>
>     <bar xmlns:p="xxx">
>        <fum xmlns:p="">
>           ...
> 
> Inside <bar> but outside <fum> there is an association of p with xxx.
> Outside <bar>, and inside <fum>, p is not associated with a namespace
> and it is a namespace well-formedness error to use it as a prefix.
> 
> > Further (and this really is strange), reading section 7 
> (Conformance), it
> > says that a document to be well-formed must match the "Namespace
> > Constraints" (in quotes). But the "namespace constraints" 
> are nowhere
> > defined, so this gives no further clues.
> 
> ???  The namespace constraints are constraints on productions, like
> the well-formedness and validity constraints in the XML spec. 
>  They are
> given in sections labelled "Namespace constraint:".  In Namespaces 1.1
> there are only two of them: "Reserved Prefixes and Namespace Names"
> and "Prefix Declared".
> 
> The second of these seems to unambiguously answer your main question:
> 
>   Namespace constraint: Prefix Declared
> 
>   The namespace prefix, unless it is xml or xmlns, MUST have been
>   declared in a namespace declaration attribute in either the
>   start-tag of the element where the prefix is used or in an ancestor
>   element (i.e. an element in whose content the prefixed markup
>   occurs). Furthermore, the attribute value in the innermost such
>   declaration MUST NOT be an empty string.
> 
> So 
> 
>   <foo>
>     <bar xmlns:p="xxx">
>       <fum xmlns:p="">
>         <p:fie/>
> 
> violates the constraint, because the innermost namespace declaration
> attribute for p is an empty string.
> 
> > It would be very useful to be able to refer to the 
> non-namespace using an
> > explicit prefix
> 
> True.  There are three things a prefix or non-prefix can mean: some
> namespace, no namespace, or an error; and only two syntaxes: a URI
> or the empty string.
> 
>                     prefix         no-prefix
> 
>     namespace       xmlns:p="xxx"  xmlns="xxx"
> 
>     no-namespace        *          xmlns=""
> 
>     error           xmlns:p=""        *
> 
> XML 1.1 introduces the xmlns:p="" possibility; there is no syntax for
> the cases marked "*".  The inconsistency of meaning of xmlns="" and
> xmlns:p="" matches the different status of prefixes and no-prefix at
> the start of a document.
> 
> > especially in a context like XSLT
> 
> XSLT was one of the uses people had in mind when they argued for
> prefix undeclaring, but they were thinking of cases like
> 
>     <xsl:copy>
>       <bar/>
>     </xsl:copy>
> 
> which can't be accurately serialized in XML 1.0 if the copied node
> has namespace bindings which <bar/> doesn't.
> 
> -- Richard
>

Received on Tuesday, 12 October 2004 17:13:42 UTC