Parsing practice (was: updates to dm mapping document)

[Norman Gray]

Gerard and all, hello.

I can't add much to your points at this stage, I don't think.  But...

On 2014 Jul 1, at 07:16, Gerard Lemson <lemson at MPA-Garching.MPG.DE> wrote:

> 4. add  a complexType, say 'VODMLAnnotation' to VOTable, with components <vodml-type> (maxOccurs=unbounded) and <vodml-role>; their usage should be obvious. This type is used for a new <vodml> (minOccurs=0) element on GROUP, FIELDref, PARAM and PARAMref. 

At the risk of a slight tangent, I wonder how disruptive such a change would actually be.

A new element such as this would of course formally make documents which used it schema-invalid.  If applications generate their XML parsing code from an .xsd file, by some magic code generator, then this could cause errors.  If, on the other hand, people construct software objects by looking for particular elements within the VOTable ("I'm constructing a GROUP; can I find any PARAM children of this element?"), then they'll probably simply ignore the novel elements.

My impression, from conversation, is that most people do in fact process XML in this by-hand style, which is effectively more permissive (and which is going to be a lot less brittle in any case), and that they don't in practice worry too much about schema-validity, other than as a way to resolve arguments, after the event.  Is that true?

[ My interest at this precise point is less in whether such a schema change is a good thing, and more whether it would have major practical effect.  I don't want to hijack this thread, so I've changed the subject line. ]

All the best,

Norman


-- 
Norman Gray  :  http://nxg.me.uk
SUPA School of Physics and Astronomy, University of Glasgow, UK