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Re: Multiple Addresses in an EPR

From: Mark Little <mark.little@arjuna.com>
Date: Sun, 16 Oct 2005 15:02:23 +0100
Message-ID: <43525D6F.8020402@arjuna.com>
To: "Conor P. Cahill" <concahill@aol.com>
CC: Mark Nottingham <mark.nottingham@bea.com>, WS-Addressing <public-ws-addressing@w3.org>

The Address element (URI) cannot necessarily be taken in isolation from 
the rest of the information within the EPR, in particular the 
ReferenceParameters. I don't know how likely it is that the same 
RefParams within an EPR will be useable with different URIs, but I'd 
guess that they're going to be tied to a specific URI - certainly that's 
the way I've seen them used in practice so far. This means that although 
it's a necessary condition to have multiple URIs for the same logical 
EPR, it's not a sufficient condition: you need to have at least the 
RefParams and maybe even the MetaData.

In your specific implementation it may be possible to say that the 
RefParams/MetaData are the same between multiple Address URIs. But 
that's an implementation choice and seems to point towards what I said 
earlier: this is better handled above the baseline WS-Addressing 
specification.

Mark.


Conor P. Cahill wrote:

>
>Mark Little wrote on 10/16/2005, 7:33 AM:
>
> >
> > I agree with the requirement. I just disagree that it's so fundamental
> > that it has to be within WS-Addressing.
>
>As far as I can tell, if you don't do this, you end up with either
>
>    a) requiring multiple EPRs,
>    b) having some elements defined in Metadata to
>       carry the same information
>    c) forcing it into a layer above addressing such
>       as within DNS or within a router
>
>a) is a pain for both the generator and expecially for the
>conumer of the EPR as they somehow have to recognize that
>the two EPRs are otherwise equal.
>
>b) is placing essentially equivalent data in two different
>locations within an EPR -- something that just seems wrong
>to me.
>
>c) can be done anyway, but then all of WS-Addressing can
>(and already is) done outside of the SOAP layer.  I presume
>that someone believes having this information in the SOAP
>layer is advantageous.
>
>WS-Addressing has chosen to define an EPR format that carries
>an address for an endpoint.  If someone is to profile that
>there are multiple physical endpoints associated with the
>logical endpoint described by the EPR, then WS-A needs
>to at least provide a location where this information is
>to be carried -- hence my request for allowing the Address
>element to be multi-occurance.
>
>Conor
>
>
>
>  
>
Received on Sunday, 16 October 2005 14:02:43 GMT

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