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Re: "Orchestration" and "Choreography"

From: Sanjiva Weerawarana <sanjiva@watson.ibm.com>
Date: Wed, 14 Aug 2002 17:41:48 +0600
Message-ID: <010301c24387$9a0dd940$c267b809@lankabook2>
To: "Anne Thomas Manes" <anne@manes.net>, <edwink@collaxa.com>, <www-ws-arch@w3.org>

Hi Anne,

Indeed. What I was saying is that IMO these terms don't have
fixed meanings in this space as they stand today. However, WSAWG
certainly can define them as you see fit.

Note that the "global model" case of Edwin's list (case 1)
does not express an executable composition - its a declaration
of how a set of services interact with each other. Only
case 2 is an executable composition - it says how to provide
a new service as a composition of two services.

Sanjiva.

----- Original Message -----
From: "Anne Thomas Manes" <anne@manes.net>
To: "Sanjiva Weerawarana" <sanjiva@watson.ibm.com>; <edwink@collaxa.com>;
<www-ws-arch@w3.org>
Sent: Wednesday, August 14, 2002 5:34 PM
Subject: RE: "Orchestration" and "Choreography"


>
> I think it's our job to make the distinction. As Edwin said there are
> different ways to assemble services. To clarify my previous comment:
>
> Orchestration: you invoke a service, and a whole bunch of other services
get
> invoked on your behalf according to the orchestration specification
> (composition of smaller services into a larger service)
>
> Choreography: you want to execute a multi-step process with another
partner.
> First you send this message to this service. He will reply with this other
> message within a certain timeframe. You next send another message to this
> other service. He will send a message to one of your services. etc. (an
> interaction script)
>
> Anne
>
> > -----Original Message-----
> > From: www-ws-arch-request@w3.org [mailto:www-ws-arch-request@w3.org]On
> > Behalf Of Sanjiva Weerawarana
> > Sent: Wednesday, August 14, 2002 4:19 AM
> > To: edwink@collaxa.com; www-ws-arch@w3.org
> > Subject: Re: "Orchestration" and "Choreography"
> >
> >
> >
> > I'm not sure whether there's such a clear distinction between
> > the terms. During the lifetime of the BPEL4WS document, it was
> > at one point called WS-Orchestration, then WS-Choreography,
> > then WS-Business Process and and eventually BPEL4WS. I can tell
> > you that the name changes had nothing whatsoever to do with
> > technical distinctions between the words .. it was all marketing
> > and, um sometimes, politics ;-).
> >
> > To me orchestration, choreography, business process, workflow
> > are all ways of indicating how to take a bunch of things and
> > put them together to do something meaningful. We also use the
> > term composition for the same thing .. BPEL4WS is a language
> > for composing a set of Web services into another service. The
> > thing that makes it a workflow language is that the composition
> > primitives chosen are those that are well-known in the workflow
> > domain.
> >
> > Edwin's distinction seems to be the difference between what
> > WSFL called global models vs. flow models. I think that distinction
> > is definitely valid (BPEL4WS doesn't yet handle global models,
> > for example), but I don't think the terms choreography and
> > orchestration distinguish between those two.
> >
> > Coordination is different IMO; that's really distributed
> > synchronization (rendezvous).
> >
> > Hope this helps,
> >
> > Sanjiva.
> >
> > ----- Original Message -----
> > From: "Edwin Khodabakchian" <edwink@collaxa.com>
> > To: <www-ws-arch@w3.org>
> > Sent: Wednesday, August 14, 2002 1:42 AM
> > Subject: "Orchestration" and "Choreography"
> >
> >
> > >
> > > Mike,
> > >
> > > There are 2 problems that need to be solved:
> > >
> > > Problem #1: You have 3 different services that
> > > interact with each other and you want to document the
> > > exchange of message between those services.
> > >
> > > Problem #2: You want to invoke 3 different services
> > > in a specific order because they have data and
> > > control dependencies between each other.
> > >
> > > Problem #1: is called choreorgraphy. It is about
> > > providing more information about interfaces of
> > > services and how they plug to each other.
> > > Choreography defines public protocols that each party
> > > needs to be compliant with. RosettaNet PIPs, WSCI,
> > > BPSS and BPEL4WS abtract processes try to address
> > > this problem. Note: This is not executable logic,
> > > only something you are compliant with.
> > >
> > > Problem #2: is called workflow, BPM or Orchestration.
> > > It is about implementing logic that ties a set of
> > > services into an end-to-end process. That logic is
> > > then executed by a run-time that dispatch the right
> > > message to the right component and wait for the
> > > reception of the right message to activate the next
> > > service. Orchestration languages are similar to other
> > > scripting language but usually include support for
> > > asynchronous interactions (<receive> in BPEL) and
> > > flow coordination ( <flow> in BPEL ) and business
> > > transactions (WS-T or BTP). Also, in term of
> > > terminology, orchestration languages use activity
> > > where traditional languages use statements.
> > >
> > > One of the most important aspect of both of those
> > > problems is that they require a visual representation
> > > because they are used as an important communication
> > > medium between partners but also within an
> > > organization between the business analyst and
> > > business users that know the rules and data models
> > > and the developers that implement the real work.
> > >
> > > my 2c,
> > > Edwin
> > >
> > >
> > >
> > > ---- "Champion, Mike" <Mike.Champion@softwareag-
> > > usa.com> wrote:
> > > >
> > > > OK, trying to eat my own dogfood here, I need help
> > > understanding the
> > > > distinctions between "coordination"
> > > and "choreography" in the web services
> > > > context.  The W3C recently acknowledged
> > > a "choreography" submission [1], and
> > > > IBM/BEA/Microsoft just unveiled a collaborative "WS-
> > > Coordination" language
> > > > [2].
> > > >
> > > > I presume that some of the authors of those
> > > documents are on this list.
> > > > Please help!  [send me private e-mail if you don't
> > > want to go on record, and
> > > > I'll sanitize/anonymize it!!!!]
> > > >
> > > > As best I understand it, "choreography" is a higher-
> > > level activity involving
> > > > multiple web service invocations,
> > > whereas "coordination" is a lower level
> > > > activity that choreography or transaction
> > > processing, security, etc. would
> > > > employ in their implementations, and could be
> > > exposed as a web service
> > > > itself.
> > > >
> > > > I have this vague sense that while REST advocates
> > > didn't express much
> > > > interest in either "coordination"
> > > or "choreography", they did so for
> > > > different reasons:  Coordination can be handled, in
> > > the REST view, by shared
> > > > "state" resources identified URI and accessed by
> > > HTTP; Choreography is
> > > > opposed on RESTful grounds so much as by the sense
> > > that
> > > > RDF/OWL/DAML-S/whatever would provide a better
> > > solution than SOAP-based
> > > > protocols.  Does anyone else see it that way?
> > > >
> > > > Special bonus question: Is there a distinction
> > > between "orchestration" and
> > > > "choreography" in the web services context?
> > > >
> > > > [1] http://www.w3.org/Submission/2002/04/
> > > >
> > > > [2] http://www-
> > > 106.ibm.com/developerworks/webservices/library/ws-
> > > coor/
> > > >
> > > >
> > > >
> >
Received on Wednesday, 14 August 2002 07:43:23 GMT

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