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"Orchestration" and "Choreography"

From: Edwin Khodabakchian <edwink@collaxa.com>
Date: Tue, 13 Aug 2002 12:42:55 -0700 (PST)
Message-ID: <200208131942.PAA25312@bellerophon.cnchost.com>
To: www-ws-arch@w3.org

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 Tuesday, 13 August 2002 15:43:05 GMT

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