Re: [xtm-wg] Comments on the syntax proposal

[Lars Marius Garshol <larsga@garshol.priv.no>]

* Lars Marius Garshol
|
| The specification should make it clear that conforming XTM 1.0
| implementations must use namespaces ...

* Sam Hunting
| 
| Forgive my density, but why?

Because otherwise it will require implementations to use the same
namespace prefixes for XTM and XLink as those used in the XTM
specification. This defeats the whole purpose of XML Namespaces and
leaves us back in the same position we were before namespaces were
conceived of in the first place.

The namespace prefix used in a document is a mere lexical detail, on
the same level as the whitespace inside a tag[1], according to the
latest XML Infoset draft. To put it another way: there is no
requirement in the XML set of standards that processing frameworks
make the namespace prefixes available to applications.

| Can't we get the semantics of xlink processing without necessarily
| having an (namespace-using) link processor?

We can, but then we run the risk of name collisions. Once namespace
prefixes are frozen the element names effectively become
'prefix:localname', rather than 'nsuri localname', which means that
the name collision guarantee provided by namespaces has evaporated.

In my opinion it would be far better to give up the use of namespaces
entirely and also remove use of XLink and XBase than to do this. As
far as I know none of the W3C XML applications (XHTML, SVG, XSLT ...)
use fixed prefixes. (See XSLT 1.0, 2.1 para 3, for example.) I think
it would cause a marketing problem in the W3C if we were to do this.
 
* Lars Marius Garshol
|
| ... and that recognition of names defined by XLink, XBase and XTM must
| be based on a namespace view of the document rather than an XML 1.0
| view. ...
 
* Sam Hunting
|
| Ditto on density, and what is a "namespace" view? What does it buy
| us that XML 1.0 processing does not?

In a namespace view element and attribute names consist of a namespace
URI and a local name, and nothing more. What it buys us I tried to
point out above.
 
* Lars Marius Garshol
|
| In other words, the namespace prefixes used in the XTM 1.0 DTD are not
| the only possible namespace prefixes for these namespaces.
 
* Sam Hunting
|
| You mean "xlink:" could change to something else? 

Yes! That is the whole point of XML namespaces.  The 'xlink:' prefix
is just a local abbreviation used in a particular document so that
URIs can be shoehorned into element type names without upsetting the
XML 1.0 syntax.

| How do we do DTD validation, then?

This is really something that the W3C should have solved for us, and
that they have not I consider a serious failure on their part. This is
by no means a difficult problem, and the XML Namespace recommendation
effectively created an XML 1.1 version that left DTDs like a useless
appendage. 
</rant>

However, since they have not, one way to do it is to use parameter
entities to combine the namespace prefixes with the local names of
elements[2]. This creates intensely ugly DTDs, but works around the
problem.  My suggestion is that we use fixed prefixes in the DTDs
meant to be read by humans, but create a special version to be used
for validation.

--Lars M.

[1] Tag, not element.

[2] Note that this needs to be done in the following manner, since PE
    references have implicit whitespace on either side when used
    outside parameter entity definitions (see 4.4.8):

<!ENTITY % xtm-prefix  "">
<!ENTITY % topic-local "topic">

<!ENTITY % topic "%xtm-prefix;%topic-local;">


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