Re: [Nml-wg] XML syntax for NML relations

16 Aug 2011

      Hi Freek/All;

On 8/16/11 7:36 AM, thus spake Roman Łapacz:
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W dniu 2011-08-16 12:09, Freek Dijkstra pisze:
...
Hi,
Hi Freek,
...
I've been thinking about the relation syntax.
So far, we have seen these two proposals:
<nml:link id="urn:ogf:network:example.net:link_A-to-C">
      <nml:relation type="serialcompound">
         ...
      </nmlserialcompound:relation>
    </nml:link>
I think you mean this instead:

      <nml:link id="urn:ogf:network:example.net:link_A-to-C">
        <nml:relation type="serialcompound">
           ...
        </nml:relation>
      </nml:link>

Your example above would not parse correctly.
...
...
and:
<nml:link id="urn:ogf:network:example.net:link_A-to-C">
      <nmlserialcompound:relation>
         ...
      </nmlserialcompound:relation>
    </nml:link>
The advantage of the first syntax is that it is very easily extendable,
and it is still obvious for a parser to understand that it is some kind
of nml:relation, even if the particular type of relation is not known by
the parser.
The advantage of the second syntax is that it is easy to create a
meaningful validator for each specific nml:relation.
I dislike both syntaxes, and was hoping for a syntax that would provide
both benefits.
If I'm correct, the following syntax will do just that:
<nml:link id="urn:ogf:network:example.net:link_A-to-C">
      <nml:relations>
        <nmlserialcompound:relation>
           ...
        </nmlserialcompound:relation>
      </nml:relations>
    </nml:link>
This adds a parent element to the relation elements, signifying that
<nmlserialcompound:relation>   is indeed a nml:relation. So even a parser
that has no knowledge about this particular nml:relation still knows
it's base syntax, while a parser that understands the details can still
use an meaningful syntax validator (such as XSD) to make sure the syntax
is correct.
The solution with namespaces gives you that (nmlserialcompound:relation
inherits from the base nml:relation). nml:relations only complicates the
xml structure without giving too much.
I agree with Roman, the use of the 'relations' element is really not 
necessary here.

I am still not clear why you believe this element is necessary.  It is a 
'grouping' concept from what I can tell, but this does not add any 
inheritance into the sub elements except that of parent/child.  The 
concept of namepsaces gives you the inheritance that I think you want.

-jason
...
Cheers,
Roman
...
Would this do, and is this syntax acceptable to all?
Regards,
Freek

Re: [Nml-wg] XML syntax for NML relations

Jason Zurawski