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RE: Typical SOA ... SOA Patterns

From: Ugo Corda <UCorda@SeeBeyond.com>
Date: Fri, 30 Jan 2004 12:02:56 -0800
Message-ID: <EDDE2977F3D216428E903370E3EBDDC9032B8A32@MAIL01.stc.com>
To: "Paul Denning" <pauld@mitre.org>, <www-ws-arch@w3.org>

> The problem I see is that WS-CDL would describe interactions 
> between busineses, but brokers might be used within one of the
> and would not have a place in WS-CDL.

WS-CDL describes interactions between services. (The concept of
"business" is not directly supported, but it could be defined in
higher-level specs that could still be built on top of WS-CDL).

So, if the broker is exposed as a service, WS-CDL should be able to
describe the corresponding interactions. Of course, if the broker is
hidden behind another service, in such a way that it is not exposed to
WS-CDL, then WS-CDL would not know of its existence.


> -----Original Message-----
> From: www-ws-arch-request@w3.org 
> [mailto:www-ws-arch-request@w3.org] On Behalf Of Paul Denning
> Sent: Friday, January 30, 2004 11:36 AM
> To: www-ws-arch@w3.org
> Subject: RE: Typical SOA ... SOA Patterns
> (See my reply to David Booth, which says this should not be 
> added as a 
> separate issue, but the agreed upon unresolved issues could 
> say something 
> about SOA.  Specifically, the issue about correlation, and 
> the issue about 
> intermediaries.)
> That's the point.
> We're talking about the "unresolved issues".
> I guess you're not grasping what I think is the unresolved 
> issue, and you 
> cannot agree that it is unresolved.
> OK.
> Perhaps "relationships between and patterns for" causes 
> confusion. So maybe simply "More work needed on SOA" would work.
> Perhaps that is obvious and will get addressed in due time by 
> W3C or elsewhere.
> I was pulled away from the F2F this week so I could not work this 
> unresolved issue in earlier.
> By the way, I was pulled away because I am working on an 
> effort which has 
> as one of its goals "to establish the value of a SOA approach 
> for xxx".
> The term "broker" gets used quite a bit in my environment 
> lately, and I 
> have been trying to define how a "broker" fits into SOA, and 
> hopefully 
> apply concepts from WSA.
> Broker was not a term I wanted to introduce to the WSA trout 
> pond.  In 
> discussions with my colleagues, we talk about simple brokers and more 
> complex brokers.  But we need to relate these "brokers" to 
> the "SOA approach".
> In WSA, we have intermediaries as an unresolved issue.  
> Intermediaries 
> could be SOAP intermediaries, or perhaps things we could call 
> brokers.  Perhaps there are different types of brokers and 
> each can be 
> identified by a role.  A broker might be a web service like 
> any other, with 
> its own WSDL and SOAP endpoint.  A broker that sits between a 
> requester and 
> some other service, in a high level view, might just look 
> like two web 
> services.  The broker may act in one role, and the actual 
> service may be 
> another role.  The broker may act as a requester for the 
> other service.  A 
> specific set of roles might be used in defining a particular 
> SOA Pattern.
> We (WSAWG) eliminated the triangle diagram from the WSA, 
> which is OK. We do not talk about the triangle diagram in the 
> section on SOA, which is OK.
> I guess I'm hoping for more clarity on SOA, in a standard would be 
> nice.  WSA says some things about discovery, registries, indexes, and 
> discovery federation, which relate to the "simple broker" 
> stuff that I deal 
> with in my day job.  I feel like I need more when it comes to 
> relating 
> complex brokers to SOA.   Given more time with WSAWG, or 
> perhaps in another 
> WG or effort, I would probably explore "SOA Patterns".  If 
> the minimal 
> essential SOA is Interface Description and Messages, then 
> adding things 
> like brokers would be a SOA Pattern; a way of using SOA.
> Maybe WS-CDL (choreography) will get into things that I am 
> calling SOA 
> Patterns.  The problem I see is that WS-CDL would describe 
> interactions 
> between busineses, but brokers might be used within one of 
> the businesses 
> and would not have a place in WS-CDL.  WS-CDL might get 
> converted to BPEL 
> for one side of the interaction, which would imply a BPEL engine (or 
> broker).  So neither WS-CDL nor BPEL may give me a view of 
> the SOA Pattern 
> used inside that organization.  I do not know enough of the 
> details of 
> either WS-CDL nor BPEL to say for sure whether or not they 
> can express SOA 
> Patterns.
> WSA section 3.4.3 says "Note that each registry or index may 
> provide a web 
> service for discovery, so it may be appropriate to use a 
> choreography or 
> orchestration description language to describe the exchanges 
> among these 
> services needed for federation."  To the extent brokers are 
> involved with 
> discovery and provide a web service interface, I may be able 
> to define the 
> exchanges in BPEL.  Brokers that deal with things like content-based 
> routing and message transformation may also have roles worth 
> defining so we 
> can use them in SOA Patterns.  Some brokers claim to do load 
> balancing and 
> failover (LB/FO).  If I have SOA, do I get LB/FO?  If minimum 
> essential SOA 
> does not provide it, what SOA Patterns do I need to get 
> LB/FO?  If there 
> are different ways of doing these things, then when a need arises to 
> combine services but not lose LB/FO, it would be nice for 
> architects to 
> have a way to articulate what they have and what they need.
> I'll start a thread over in ws-chor to see if/how they are 
> addressing any 
> of this.
> Paul
> At 11:55 AM 2004-01-30, Cutler, Roger (RogerCutler) wrote:
> >In my humble opinion it is too late.  Even though I would probably 
> >support such a statement (if I understood it), I think that 
> it is VERY 
> >clearly substantive and beyond the scope of mechanical 
> preparation for 
> >publication.  I think that it would be a VERY bad precedent 
> to sneak a 
> >substantive change in after the WG has disbanded.  In 
> addition, I think 
> >that the fact that as a former member of the former working group I 
> >honestly do not understand what the statement means or the 
> >ramifications of it indicates that discussion would have 
> been required 
> >had it been proposed during the working session of the group.
> >
> >Sorry.
> >
> >-----Original Message-----
> >From: www-ws-arch-request@w3.org 
> [mailto:www-ws-arch-request@w3.org] On 
> >Behalf Of Paul Denning
> >Sent: Friday, January 30, 2004 10:40 AM
> >To: www-ws-arch@w3.org
> >Subject: RE: Typical SOA ... SOA Patterns
> >
> >
> >
> >At 10:20 AM 2004-01-30, Champion, Mike wrote:
> > >I completely agree.  The problem is that it is January 
> 30th; the WG 
> > >charter ends tomorrow, and we are simply out of time to make *any* 
> > >substantive changes to the Note.  (Typos, broken links, 
> etc. can be 
> > >reported and fixed until Wednesday, I believe).
> >
> >I guess it is up to the editors to add verbiage (perhaps, or do 
> >something with @@) in section 4.3 [1], which now reads
> >
> >4.3 Significant Unresolved Issues
> >
> >@@What is the difference between an MEP and a Choreography?
> >
> >@@What should be the representation returned by an HTTP 
> "GET" on a Web 
> >service URI?
> >
> >@@Should URIs be used to identify Web services components, 
> rather than 
> >QNames?
> >
> >@@The relationship between privacy and Web services technology needs 
> >clarification.
> >
> >@@SOAP 1.2 and this architecture introduce the concept of 
> >"intermediaries", but this concept is not represented in WSDL 2.0.
> >
> >@@[wordsmith:] What happens if two WSDL documents define the same 
> >service?
> >
> >@@The relationship between conversations, correlations and 
> transactions 
> >and choreography is unclear and needs more work.
> >
> >@@There is a need for consistent tracking mechanisms in Web services.
> >
> >------
> >I am proposing
> >
> >@@Further work on the relationships between and patterns for 
> using Web 
> >services and SOA.
> >
> >(Would be nice to add it if we can, but I understand if it is too 
> >late.)
> >
> >[1] 
> >http://dev.w3.org/cvsweb/~checkout~/2002/ws/arch/wsa/wd-wsa-a
Received on Friday, 30 January 2004 15:03:21 UTC

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