- From: Jon Dart <jdart@tibco.com>
- Date: Wed, 19 Mar 2003 09:09:42 -0800
- To: "Burdett David" <david.burdett@commerceone.com>
- CC: "'Patil Sanjaykumar '" <sanjay.patil@iona.com>, "'Martin Chapman '" <martin.chapman@oracle.com>, "'public-ws-chor@w3.org '" <public-ws-chor@w3.org>
I am with Martin here: I thought we agreed at the F2F not to try to define orchestration. Re the other proposed glossay terms, I do envision a glossary being part of the output of this group (or at least additions to the WSA glossary), but my understanding is that the near-term deliverable is a requirements doc. So I'd like to suggest that the priority should be to capture that part of the F2F + recent email discussion that bears on requirements. --Jon Burdett, David wrote: > I think that doing a summary could be very useful as I think there is > distinction, as Sanjay describes below, between the individual and > global views which is at the essence of the difference between > orchestration and choreographies and on which I think, if you had time > to follow all the emails on the topic, there was a fair degree of consensus. > > So how about if Assaf and I, together with anyone else who wants to > contribute, go off-line, write up the differences and then publish to > the list in the near future. It would also significantly reduce the > "noise" on the list. > > Anyone disagree? > > David > PS I am having problems sending emails remotely from my laptop and can't > work off-line, so I cannot easily respond to emails - perhaps that's > good news ;-) > > -----Original Message----- > From: Patil, Sanjaykumar > To: Martin Chapman > Cc: public-ws-chor@w3.org > Sent: 3/18/2003 3:29 PM > Subject: RE: Definition of Terms > > Sorry to belabor this point, but do we see value in clearly > distinguishing the two different entities, that is the global view vs. > the individual participant's view, which the discussion on orchestration > vs. choreography was getting at. > > I am not entirely sure if the envisioned summary on this topic would > also account for the issues with the internal vs. external choreography, > but to me, the discussion sounded very similar. Others, any comments? > > Sanjay Patil > Distinguished Engineer > sanjay.patil@iona.com > ------------------------------------------------------- > IONA Technologies > 2350 Mission College Blvd. Suite 650 > Santa Clara, CA 95054 > Tel: (408) 350 9619 > Fax: (408) 350 9501 > ------------------------------------------------------- > Making Software Work Together TM > > -----Original Message----- > From: Martin Chapman [mailto:martin.chapman@oracle.com] > Sent: Tuesday, March 18, 2003 3:10 PM > To: Patil, Sanjaykumar; 'Assaf Arkin'; 'Burdett, David' > Cc: ChBussler@aol.com; public-ws-chor@w3.org > Subject: RE: Definition of Terms > > > see my previous mail. I thought we had agreed not to make any > distinction for the time being. > > Martin. > > -----Original Message----- > From: public-ws-chor-request@w3.org > [mailto:public-ws-chor-request@w3.org] On Behalf Of Patil, Sanjaykumar > Sent: Tuesday, March 18, 2003 1:01 PM > To: Assaf Arkin; Burdett, David > Cc: ChBussler@aol.com; public-ws-chor@w3.org > Subject: RE: Definition of Terms > > > > David/Assaf, would it make sense to capture these definitions (at least > the ones for orchestration and choreography) in a document? We could > even use the set of characteristics that David listed in his original > email to highlight the differences between orchestration and > choreography, perhaps in a tabular form. Once again, I am personally > keen on clearly distinguishing the two conceptual areas and it doesn't > matter to me much which words we stick to them. > > I am sure there are others on the list who would prefer to review the > summary of this discussion before making any further comments! Chairs, > any thoughts? > > Sanjay Patil > Distinguished Engineer > sanjay.patil@iona.com > ------------------------------------------------------- > IONA Technologies > 2350 Mission College Blvd. Suite 650 > Santa Clara, CA 95054 > Tel: (408) 350 9619 > Fax: (408) 350 9501 > ------------------------------------------------------- > Making Software Work Together TM > > -----Original Message----- > From: Assaf Arkin [mailto:arkin@intalio.com] > Sent: Tuesday, March 18, 2003 12:51 PM > To: Burdett, David > Cc: ChBussler@aol.com; Patil, Sanjaykumar; public-ws-chor@w3.org > Subject: RE: Definition of Terms > > > You'll have to excuse me for confusing people again. I also think of > choreography in terms of roles, so it can support any number of > services, but most of the time when I write down examples I use the term > service. I did mean what you said and said not what I mean ;-) > > arkin > > -----Original Message----- > From: Burdett, David [mailto:david.burdett@commerceone.com] > Sent: Tuesday, March 18, 2003 12:36 PM > To: Assaf Arkin; Burdett, David > Cc: 'ChBussler@aol.com'; sanjay.patil@iona.com; public-ws-chor@w3.org > Subject: RE: Definition of Terms > > > > Assaf > > I agree with your response completely, but with one exception. > > Choreographies should be expressed in terms of roles not services, e.g. > > Role J > activity A1 send request > > Role K > activity A2 receive request > > I think this is important as it enables reuse of the choreography > definition, to take a more realistic example .. > > Buyer > activity order send request > > Seller > activity order receive request > > If you don't use roles then you would have . > > ABC Co Buyer service > activity order send request > > XYZ Inc Selling service > activity order receive request > > ... and every interaction done in business would each have its own > separate choreography. This won't scale. > > Choreography really should be abstract in order to enable reuse. This > also applies to the message definition as well as the service. > > Thoughts? > > David > > > > -----Original Message----- > From: Assaf Arkin [ mailto:arkin@intalio.com <mailto:arkin@intalio.com> > ] > Sent: Monday, March 17, 2003 11:58 PM > To: Burdett, David > Cc: 'ChBussler@aol.com'; sanjay.patil@iona.com; public-ws-chor@w3.org > Subject: Re: Definition of Terms > > > Burdett, David wrote: > > > Christoph > > > > See comments inline below. > > > > David > > > > -----Original Message----- > > *From:* ChBussler@aol.com [ mailto:ChBussler@aol.com > <mailto:ChBussler@aol.com> ] > > *Sent:* Monday, March 17, 2003 9:44 PM > > *To:* david.burdett@commerceone.com; sanjay.patil@iona.com; > > public-ws-chor@w3.org > > *Cc:* ChBussler@aol.com > > *Subject:* Re: Definition of Terms > > > > Hi, > > > > a remark on 'control' (or maybe a question). I assume that your > > definition of 'message' is abstract, i.e. does not imply > > asynchronous transmission between sender and receiver. > > [David Burdett] Right. A message is completely abstract. It is > > simple the transmission of information from one location to > > another (e.g. from one service to another). How this transmission > > is achieved is immaterial, i.e. it can be eith synchronous or > > asynchronous - whatever those words mean. In fact on the WSA group > > > there has been great difficulty and debate around defining what > > synchronous and asynchronous actuall mean [1]. > > > I would tend to define a message as a container of information. The > container notion is important because it lets you compose different bits > > of information that can be reused in different messages, and different > bits of information may have different significance (e.g. the business > request, the topic of request, the requesting party). WSDL does that > pretty well. > > The message definition is that of a message at rest. It says nothing > about which direction it goes on, or which service can consume or > produce it. That information is provided by the operation. The operation > > tells you whether that message is an input or an output, and in fact > what it signifies. The action then tells you which service is > responsible for performing that operation either as the requestor or > provider, and in relation to all other actions. > > > > The definition of 'control' in general is difficult. Maybe a > > distinction has to be made between controlling the definition vs. > > controlling the execution (i.e., type vs. instance). > > [David Burdett] Very true. A choreography definition (the type) > > is, IMO, something that MUST have an independent existence and be > > agreed by all the roles involved before interoperable solutions > > can occur. The actually choreography *definition* must also be > > owned by someone as it is a single definition that describes what > > all the roles must do. For example, in B2B, the owner of a > > choreography definition could be: a) an 800lb Gorrilla, e.g > > Walmart telling all its suppliers follow the Walmart choreography > > or you don't do business, b) a trade association, e.g. RosettaNet > > with their PIPS, or c) an international standards organization, > > e.g. UN/CEFACT. > > On the other hand, the execution of a choreography can be owned by > > > no one and HAS to be handled by mutual agreement, even if it > > is the SME agreeing to do business the way Walmart wants them to! > > > I think that the use of the term 'domain of control' depends on context. > > We can talk about who owns the definition, who runs the instance, even > who serves the coffee. But I think there's a very clear and precise > meaning in terms of choreography. > > Let's say that some service X sends a message (request) to service Y, > service Y receives that message, does something and then sends back a > response. Service X performs some activity A1 which sends the message. > Service Y performs some activity A2 which receives the message, and > later on some activity A3 which sends back a response. Service X and > service Y belong to different domains of control. > > Service X can't just start an activity in service Y by wishful thinking. > > And ESP technology is not proven yet. So service X "coerces" service Y > to start an activity by sending it a message. Service Y needs to perform > > two activities one after the other. Service Y has some unspecified means > > to do that, maybe because it has a big piece of Java code, or because it > > uses some internal mechanism to chain these activities together. But > it's not important to express how these activities are chained together > in the context of a choreography. > > So in the choreography we would say something like: > > service X > activity A1 send request > > service Y > activity A2 receive request > > We show the relation between two activities executing in different > domains of control by expressing how they communicate, which is > important information for both services to understand. > > On the other hand, the choreography definition of service Y could say > something like: > > service Y > activity A2 receive request > activity A3 send response > > Exactly how service Y chains these two activities together is not > interesting for service X (or any other service in the choreography). > It's an implementation detail. Service Y may have some other message > that is send by A2 to start A3, or it may update some record in the > database, of have some person flicking switches on a big panel. That's > not important. > > We show the relation between two activities executing in the same domain > > of control using some form of sequencing that does not require explicit > form of communication, e.g. in a procedural way, using state transition > diagrams, or by expressing a process flow > > (WSCI takes the third approach since it makes it easier to model > activities that occur in parallel. Unfortunately, due to the choice of > syntax - and I'll be first to take the blame - it is often confused with > > being procedural and non-cyclic despite the intent of the authors) > > arkin > > > > > Thanks, > > > > Christoph > > > > [David Burdett] [1]See, for just one example, the thread starting > > at > http://lists.w3.org/Archives/Public/www-ws-arch/2003Mar/0074.html > <http://lists.w3.org/Archives/Public/www-ws-arch/2003Mar/0074.html> > > > > In a message dated 3/17/03 4:55:50 PM Pacific Standard Time, > > david.burdett@commerceone.com writes: > > > > > > > -- > "Those who can, do; those who can't, make screenshots" > > ---------------------------------------------------------------------- > Assaf Arkin arkin@intalio.com > Intalio Inc. www.intalio.com > The Business Process Management Company (650) 577 4700 > >
Received on Wednesday, 19 March 2003 12:10:32 UTC