SV: [ubl-dev] UBL- just how reliable are XSD based syntax checks?

["Bryan Rasmussen" <BRS@itst.dk>]

>Simple XML without namespaces - like it or not - is a lowest common
>denominator, for both tools and people.  I know that will be processed
>by a simple lightweight XML processor, or import / export feature.
I can agree with that, with the note that every XML processor that I know of
that will not handle XML Namespaces in a manner the correctness of which I
have not had occasion to question (and the only time I ever questioned the
handling of an XML namespace by a processor I was wrong anyway) is an XML
processor that is does not follow the XML spec by itself. The one that comes
to mind offhand is Rebol's built in processor, but I have seen similar
processors in various lisp-y languages. This can be useful when you want to
write a processor for RSS or similar standards with 'unimportatn' data, but
other than that I don't think it is useful. 
Note, I have heard that SAP has problems with long namespaces. 

 

> UBL fortunately is not in that bucket - but plenty of other XML is -
>with conflicting default namespaces, inline namespaces and duplicate
>and invalid namespace declarations. 
hmm, I can think of some XSLT processor errors in the way they handle
namespaces, but this is dependent on the XSL-T spec not on namespaces. What
you are saying sounds like basic irritating aspects of namespace scoping, are
there processors that mismanage these things?

I mean it sounds to me you are complaining about stuff like this 
<?xml version="1.0"?>
<!-- initially, the default namespace is "books" -->
<book xmlns='urn:loc.gov:books'
      xmlns:isbn='urn:ISBN:0-395-36341-6'>
    <title>Cheaper by the Dozen</title>
    <isbn:number>1568491379</isbn:number>
    <notes>
      <!-- make HTML the default namespace for some commentary -->
      <p xmlns='http://www.w3.org/1999/xhtml'>
          This is a <i>funny</i> book!
      </p>
    </notes>
</book>
from the spec. I can see why one might complain but it is what I've always
understood and experienced as perfectly allowable.

Do you have examples where a processor accepts bad namespaces? 
This reminds me of Joe English's psychology of namespaces screed  some years
back: http://lists.xml.org/archives/xml-dev/200204/msg00170.html



>CAM is able to read in bad namespaced content and fix it and create
>better namespace declarations for you so it processes with XPath
>expressions that work correctly.

I might find any tool automating namespace changes for me scary. I want to be
able to say change all namespaceX to namespaceY then run namespaceY handling.



>The fact that CAM can handle that content with or without those
>namespaces - interchangably - clearly something that does not interest
>you - but may be of convenience to implementers.
Well I don't know that I would argue that UBL needs namespaces in the form
they are in now, but I think for any large dialect Namespaces are really
beneficial, especially if we want to extend the dialect or want others to
extend their dialects with ours. 
Basically I think the complexity of UBL namespaces is dependent on some of
the irritating aspects of using XML Schema as a validation language.



>Contrary wise - seems that you are OK with using downstream feeds that
>collect data that ultimately ends up being packaged in real UBL - as a
>convenience - just so long as those downstream feeds are not labelled
>as "UBL".

I think everyone is okay with that.

Cheers,
Bryan Rasmussen