Re: [Ecrit] Profiles (was: Consensus Call) - namespaces

[Andrew Newton <andy at hxr.us>]

On Apr 27, 2007, at 10:35 PM, Henning Schulzrinne wrote:

> This concrete example is helpful.
>
> Since applications such as LoST don't typically do schema  
> validation, maybe it's more helpful to look at what an application  
> would actually do, such as using SAX and DOM.
>
> Clearly, the application only has a limited repertoire of XML tags  
> that it recognizes and then parses. It will presumably build up its  
> internal data structure from those elements.
>
> There are two cases:
>
> (1) Senders can only generate certain orderings of elements, such  
> as Point followed by civicAddress, even though the schema allows  
> any ordering. A 'profile' specifies this.
>
> (2) Any ordering permitted by the schema can appear in the XML  
> document.
>
> Doing (1) simplifies processing, since there are fewer elements  
> that can occur at any given time, but with an event-based or DOM- 
> based model, it doesn't seem to make a whole lot of difference.

There was a leap in logic to "doesn't seem to make a whole lot of  
difference" that I don't understand.  As far as ingesting the data in  
to data structures, yes.  As far as recognition of the semantics, the  
server is still left to attempting to figure out what profile the  
sender is using without any hints.

Given your logic, you could argue that XML namespace declarations are  
completed unneeded as applications should be able to know that when  
tag <foo> always precedes tag <bar>, they are dealing with tags from  
the http://example.com/foobar namespace.

> We obviously do want to restrict the GML elements that can occur in  
> the XML sent, but that's a standardization issue, not a labeling  
> issue. Thus, I'm all in favor of defining profiles for the sender.

We are in agreement here.

> I just don't see how a profile label (beyond the namespace  
> indications) would simplify the processing or improve error  
> processing.

Because, it would allow the sender to tell the server which profile  
it was sending.  Since neither of us seem to be advocating XML  
validation in this case, I be happy to compromise and say that  
senders do not have to include the profile identifier if they don't  
know it.  Is that workable?

-andy

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