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RE: Definition of Terms

From: Patil, Sanjaykumar <sanjay.patil@iona.com>
Date: Mon, 17 Mar 2003 16:04:28 -0800
Message-ID: <EA3ECEFACBE7674789ADE4D9E3ABB6B03E18F3@AMERWEST-EMS1.IONAGLOBAL.COM>
To: "Burdett, David" <david.burdett@commerceone.com>, "WS Choreography (E-mail)" <public-ws-chor@w3.org>


Frankly speaking, it's still not clear to me what the differences are (or how we want to define the differences for our convenience) between orchestration and choreography (and it seems we have to also deal with: process, conversation, interaction, interaction instance!).

David, this is what I am interpreting from your definitions. Please let me know if I am wrong ...
Choreography provides the global view, where as the scope of orchestration is confined to any single entity participating in the choreography! Expanding the concept further, as per your definition, an orchestration is constrained by the roles it plays (that are defined by choreographies) and the other orchestrations it interacts with.

I remember somebody distinguishing these two terms in another way during the F2F, by associating liveliness with them, that is, choreography is a definition where as orchestration is an execution of the definition!

I also remember we simply abandoning the use of the term "orchestration" in order to move on!!

What I really carried with me on this topic in the F2F was somebody's comment that:- let us first nail down the concepts that we want to define and then we can associate any terms with those concepts. That is, let us first define the problems we want to deal with (I guess this is where we got into the internal vs external debate!!).

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
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Making Software Work Together TM


-----Original Message-----
From: Burdett, David [mailto:david.burdett@commerceone.com]
Sent: Monday, March 17, 2003 2:34 PM
To: WS Choreography (E-mail)
Subject: Definition of Terms



Folks
There has been a lot of discussion about Choreographies, Orchestrations,
Conversations, etc, so I thought it might help to make an attempt at some
definitions of terms so that the distinction between them all was clear.
The following is my attempt. It starts with some very basic definitions on
which later definitions rely. I am also certain that there is still plenty
of scope for improvement and revision, so comments are welcome.
Hope this helps.
David
=========================================
INFORMATION 
Information is data of a specific type, for example, "Order Information",
"Status Information". Information has a specific semantic meaning, e.g.
"Order Information" is a  "request to purchase goods". The same piece of
Information can take many different forms, for example an XML, PDF, email,
paper letter, fax, voice, etc. 
MESSAGE 
A Message is a description of one or more pieces of Information combined
with adressing information. A Message can have one or more different Message
Representations.
MESSAGE REPRESENTATION 
A Message Representation is a definition of the binding of a message to a
particular form, for example each of the following are Message
Representations: a UBL Order schema defintion within the Body of a SOAP
Message, an EDI Order document within an ebXML Message or a spoken voice
description of an Order. 
MESSAGE INSTANCE 
A Message Instance, is an instance of an actual Message Representation, e.g.
a real UBL order expressed in XML with real line items inside a SOAP
message, etc. 
LOCATION 
A Location is a description of a person, place, software, application or
service that can generate or accept Message Instances. A Location may accept
or generate Message Instances in one or more different Message
Representations. (In WSDL this would be a Port). 
ROLE 
A Role is a description of a set of related Processes that serve a single
purpose. For example a "buyer role" is the set of activities taken by a
party, individual, business or software that are required to purchase goods.
A Role may be supported at multiple Locations. A Location may support
multiple Roles. 
INTERACTION 
An Interaction is the definition of the sending of a Message from one Role
to one other for a reason. For example: a) sending an "order message" from a
"buyer role" to a "supplier role" so that the "supplier role" can satisfy
the order, or b) sending an order message from an "archive requesting role"
to an "archive "archiving accepting role" so that the latter role can
archive the order message. 
INTERACTION INSTANCE 
An Interaction Instance is the sending of one Message Instance from one
Location acting in one Role to another Location acting in another Role. 
PROCESS
A Process is the description of a set of activities that do useful work that
occur as a result of an event such as the arrival of a Message Instance or
the passage of time. The execution of a Process usually results in the
generation of additional Message Instances. 
SUB-PROCESS 
A Sub-Process is a Process that is executed as part of and under the control
of another Process. 
CONTROL DOMAIN 
A Control Domain is a description of the set of Processes that are under the
management control of a single entity or organization. The Processes and the
Sub-Processes that are within a Control Domain can only be changed or
altered by the entity that manages them. A Control Domain can support one or
more Roles. 
COLLABORATIVE PROCESS 
A Collaborative Process is a Process that is implemented through
Interactions between two (or more) Roles within two (or more) Control
Domains. 
CHOREOGRAPHY
A Choreography is the definition of the sequence and dependencies of the
Interactions between Roles required to implement a Collaborative Process.
For example the process by which a "buyer role" places an order with a
"supplier role", or the process by which a procurement system comunicates
order information with an ERP system. 
ORCHESTRATION 
An Orchestration is the definition of the sequence and dependencies of the
Processes executed by a single Role. The Interactions that result from
executing the Processes MUST comply with: a) any constraints implied by any
Choreographies in which the Role takes part, and b) any constraints on
Message Representations that Locations that receive Message Instances
generated by the Orchestration require. 
All the Processes and Sub-Processes within a single Orchestration definition
should be related to one another. An Orchestration definition may be used to
define the behavior of a Process that is executed by a single Role. 
CONVERSATION 
A Conversation is an instance of the execution of a Choreography or an
Orchestration. 

Thoughts?

Director, Product Management, Web Services
Commerce One
4440 Rosewood Drive, Pleasanton, CA 94588, USA
Tel/VMail: +1 (925) 520 4422; Cell: +1 (925) 216 7704
mailto:david.burdett@commerceone.com; Web: http://www.commerceone.com
Received on Monday, 17 March 2003 19:05:05 GMT

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