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RE: ISSUE 8 : "Clarity and Safety"

From: George Datuashvili <George.Datuashvili@Siebel.com>
Date: Tue, 9 Nov 2004 16:17:23 -0700
Message-ID: <A848DF40DD990243BA95891B80069D4107B0BEC2@SDCEXMB01.corp.siebel.com>
To: "Glen Daniels" <gdaniels@sonicsoftware.com>, public-ws-addressing@w3.org

Great description of problem. Issue of "other" headers overlapping
reference properties has been bothering us too :) On another hand this
weakness can be a strength in some cases.

One nice aspect of wrapper-less processing rules is that you can
instruct sender to provide headers for intermediary that knows nothing
about WS-Addressing. As a consequence you can to some degree compose use
of other specifications with WS-Addressing without adding spec-level
dependancy.


> -----Original Message-----
> From: public-ws-addressing-request@w3.org 
> [mailto:public-ws-addressing-request@w3.org] On Behalf Of Glen Daniels
> Sent: Monday, November 08, 2004 10:46 PM
> To: public-ws-addressing@w3.org
> Subject: ISSUE 8 : "Clarity and Safety"
> 
> 
> 
> Here's a start at issue 8, and a clarification of some stuff 
> I wrote about issue 11.  Upon another read of [1], I think 
> that was a pretty good summary, actually.  However, I'll 
> endeavor to go a little further here.  I'll split these out 
> into separate emails for easier discussion.
> This one is about "Clarity and Safety".
> 
> Let's consider a refP as follows (namespace mappings are assumed in
> examples):
> 
>   <epr>
>    <refps>
>     <wsse:Security>
>       ...
>     </wsse:Security>
>    </refps>
>   </epr>
> 
> This would result in a static wsse:Security header appearing 
> in a message to this endpoint, as a result of following the 
> rules for refp's as they stand.  This header might be a) 
> wrong with respect to the rest of the message, or b) a 
> duplicate.  Another example:
> 
>   <epr>
>    <refps>
>     <admin:ShutDown/>
>    </refps>
>   </epr>
> 
> The thrust of thes particular cases involves an error (either 
> happenstance or malicious) on the part of someone supplying 
> an EPR, and of course we cannot protect against all such 
> situations.  However, the current design forces such errors 
> (bad refps) to happen at the SOAP infrastructure layer, as 
> opposed to inside the WSA module of an implementation.  This 
> has a few implications.
> 
> First, a layering problem - if I am to protect against such 
> errors, my infrastructure should probably scan all my refp's 
> to make sure they don't step on the toes of some "real" SOAP 
> extension.  One might argue that this isn't necessary, and 
> that you should just "trust the source of the EPR", but I 
> disagree - one could make the same argument against checking 
> for nulls/bad data in methods on a C# or Java object.  If you 
> provide a way for data (EPRs) that affects your SOAP 
> processor to be supplied by the outside world, you open 
> yourself up to errors in that data affecting your SOAP node 
> in potentially unclear ways - especially since refp's lose 
> their "refp-ness" once they get "header-ized". (this is the 
> "safety" part)
> 
> Second, if some node (either an intermediary who has no 
> knowledge of the EPR in question or maybe even the endpoint) 
> has a problem with one of these refps, it becomes harder to 
> debug what's going on when you account for the fact that any 
> of the headers might have been inserted due to processing an 
> EPR instead of due to actually following some extension's 
> contract.  In many (most?) modern SOAP processing systems, 
> there are going to be code modules which are responsible for 
> processing extensions.  In general each of these modules is 
> going to be directly responsible for a small subset of 
> headers.  Having a WSA module be required to insert an 
> arbitrary number of arbitrary headers may make it much less 
> clear where things are coming from, and which code to examine 
> when there is a problem. (this is the "clarity" part)
> 
> I would put forth that the SOAP processing model actually has 
> two sides to it.  The first is the one we're all familiar 
> with, i.e. what nodes must do when processing a message 
> containing headers.  The other side, though, is that the 
> *originator* of a given message actually inserted some SOAP 
> headers, and therefore by virtue of that fact, they agreed to 
> the semantics of those headers.  If WSA allows, or rather 
> forces, us to insert arbitrary headers which are explicitly 
> opaque, we change that part of the SOAP contract in what I 
> believe are at least confusing, and possibly dangerous, ways.
> 
> Proposal:
> 
> I would like to have the group consider the ramifications of 
> sending the refp's inside another element, whether that be 
> <wsa:To> or a separate <wsa:RefPs> header.  In either case, 
> the same exact information would be available to the SOAP 
> node (I am intentionally not saying "the application" to 
> avoid implementation-specific layering assumptions) as in the 
> case where each refp was a separate header, except there 
> would be a well defined semantic that <wsa:RefPs> (or 
> whatever name) contains a bag of data that is meant to go 
> along with each message sent to this endpoint.  This would 
> solve the problems I mention above (and others - see other 
> threads), and as far as I can tell would not lose us anything.
> 
> Thanks,
> --Glen
> 
> [1]
> http://lists.w3.org/Archives/Public/public-ws-addressing/2004N
> ov/0008.ht
> ml


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Received on Wednesday, 10 November 2004 01:18:20 GMT

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