W dniu 2012-02-17 16:28, Freek Dijkstra pisze:
Hi all,
A port can have many properties. It can be abstract, Ethernet, (NSI) domain boundary port, have restricted access, be part of a link bundle.
What I want to avoid is having to deal with namespaces and objects such as<nml-nsi-ethernet-restricted-lacp:port>
If we allow adding new tags as extensions in any place in the structure then we don't have too much control over the structure. Generic parsers will not know how to interpret such unexpected (not included in the base NML schema) changes. On the contrary, namespaces as extensions allow parsers to, at least, understand their standard properties, others would be ignored. The structures defined in the base NML schema are still followed. (Of course it is possible to define a schema in such way that any element could be inserted in any place but I don't think it's the right direction). The RNC schema you created last year DID allow arbitrary elements inside NML elements.
I think I misunderstand you. In particular, I do not understand the sentence "namespaces as extensions allow parsers to, at least, understand their standard properties."
a very simple example <nml-ext:x> <nml:y></nml:y> <nml-ext:z></nml-ext:z> </nml-ext:x> A parser which does not understand the nml-ext extension/namespace would treat x as nml:x (of course if nml:x exsits) and ignore nml-ext:z. Roman
Are you talking about chameleon namespaces?
I assume that:
* NML elements can contain arbitrary child elements, from the NML or other namespace * if a parser encounters an unknown element from a known namespace, it should stop and return an error * if a parser encounters an element from a unknown namespace, it should ignore it (or -if we define chameleon namespaces- interpret as if it was part of the base namespace) (Note that in this case, I'm unclear how a parser should distinguish between a chameleon namespace and a proprietary namespace which can safely be ignored.)
Could you perhaps give an example of a message containing NML and NSI information, and explain how a parser which only understands NML sees it, and how a parsers understands both NML and NSI sees it, and if either should ignore unknown elements or stop and return an error?
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