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Re: WS-RA issue 9700 disposition

From: Doug Davis <dug@us.ibm.com>
Date: Fri, 14 May 2010 08:24:07 -0400
To: antoine.mensch@odonata.fr
Cc: "public-ws-resource-access@w3.org" <public-ws-resource-access@w3.org>, "public-ws-resource-access-comments@w3.org" <public-ws-resource-access-comments@w3.org>
Message-ID: <OFF22295AC.10CFAC0B-ON85257723.00412290-85257723.004424F8@us.ibm.com>
Antoine wrote on 05/14/2010 03:37:33 AM:
> > > I am still not convinced that the existing mechanisms will allow us 
> > > profile out the Content attribute in DPWS servers: I agree that 
> > > the attribute is optional and has a default value of ".../Any" it is
> > > easy to profile out its use in DPWS clients, but it is not enough.
> >
> > You're correct that a service _will not_ be able to profile out the
> > Content attribute.  The WG discussed this and it was felt that 
> > a service to not support the Content attribute would revert the spec 
> > back to its
> > old state which wasn't optimal.
> Maybe not for you, but it was perhaps optimal for device vendors who 
> have been implementing this spec for 5 years in 512 KB of Flash and 96 
> KB of RAM (and yes that's kilobytes, not megabytes, including OS, 
> middleware and applications). I am not against making the life of the 
> client easier, but it shouldn't be at the expense of making the life of 
> the server impossible.

Its a balancing act. You may need to expand on this a bit for me because
mex isn't requiring people to support any Content URI that they don't want 
so from a server perspective it might require additional IF statements to
ensure the client is only asking for what the server can support but that
doesn't seem like asking too much.

> > > Should it look at the WS-Policy assertion (thus making it kind of
> > > mandatory, and also creating a bootstrap problem)?
> >
> > Ideally yes.  :-)  that's why its there.  If people choose not to use 
> > recommended advertising approach there isn't much we can do.
> Policy assertions are not always easy to get and extract from their 
> enclosing document, especially in the case of WS-Mex policy assertions, 
> as you need to figure out how to get them out-of-band (bootstrap 

Getting WS* Metadata in general isn't the easiest, that's for sure.
But (and this is just my opinion) I think now that MEX has the GetWSDL()
operation it should at least make sure that everyone has the same single
starting point for getting the stuff they're interested in.  So, doing
a GetWSDL() should return a WSDL doc that contains the MEX assertion
with the data you're looking for.  Yes there might be references in there
instead of the data itself, but at least we know where those should be.
As for bootstrapping, I'm hoping people get into the habit of placing
the MEX assertion into EPRs they pass around.

> > True, but there were a couple of concerns with this that the WG 
> > discussed:
> > - this is, in essence, creating another advertising mechanism.  Having 

> > both
> > policy and this seemed redundant.
> It can also be called a redirection/negociation mechanism, a bit like 
> the 3xx codes in HTTP, which some people find useful. Also, policy 
> applies to each dialect (class-level information), while the 
> mex:AlternateContent would apply to each individual instance 
> (resource-level information), so I don't think it would be that 

re:3xx - sort of.  Although, that works at a different level (the entire 
doc and not
a sub-resource of the doc), and 3xx is telling you where to go to get the
doc you asked for, not where to go to get something similar.  But I do
understand your point and I'm sympathetic to it - the WG just couldn't
get past the fear of the added complexity they saw.

> > - while this seems like a nice benefit for those clients that will 
> > want to
> > issue a secondary request, it creates a bit of noise for those clients 

> > that
> > do not want this information.  Akin to "why are you telling me you 
> > oranges when I asked for apples?"
> Well to expand on the metaphor, if you go to your grocer's shop and ask 
> for apples, the guy is very likely to offer you oranges instead if he 
> doesn't have apples, and if you're really hungry, you're going to buy 
> them! ;)

LOL probably true - but if I was hungry (which I am right now) I'd 
turn around and ask what else they had ("Any") w/o needing to be prompted,
or being the picky eater that I am, I'd probably ask about the
smaller list of things that I'm willing to choke down.  :-)

Received on Friday, 14 May 2010 12:24:55 UTC

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