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Re: Relationship cardinalities (was ... RE: Requirements: Decisio n Po ints Requirement Proposals

From: Assaf Arkin <arkin@intalio.com>
Date: Tue, 10 Jun 2003 11:56:43 -0700
Message-ID: <3EE629EB.4070909@intalio.com>
To: "Burdett, David" <david.burdett@commerceone.com>
CC: "'Martin Chapman'" <martin.chapman@oracle.com>, "'Jean-Jacques Dubray'" <jjd@eigner.com>, "'Yaron Y. Goland'" <ygoland@bea.com>, "'WS Chor Public'" <public-ws-chor@w3.org>

When I build a system to participate in a choreography what role it 
takes has no meaning to me unless the role also says what it should do 
or expect other participants to do. Essentially, I need a definition of 
its commitments. If the commitments are similar across two 
choreographies then that system can participate in both of these 
choreographies. If the commitments are widely different but they so 
happen to have the same name, it really doesn't help the system 
participate in more than one choreography.

So again, it boils down to: is the role just a fancy name, or is there 
more information associated with that role, and in this case, can we 
define that information specific for the role and use it to define any 
number of choreographies?

arkin

Burdett, David wrote:

>Assaf said ...
>
>  
>
>>>>I assume what you mean by same role is not the fact that both
>>>>        
>>>>
>choreographies choose to call it 'buyer', but the fact that in both of them
>the buyer would be able to act in the same way against the seller. <<<
>I really mean that a buyer can act in *different* ways with a seller, i.e.
>different choreographies, for the same purpose, e.g. placing an order.
>
>  
>
>>>>In that case, would it make more sense to define the buyer's participant
>>>>        
>>>>
>and then create two choreographies using that reusable definition?<<<
>
>I'm not sure what you mean by buyer's participant. I really think that you
>need to define the roles and then identify the role being taken by a
>participant in an instance of a choreography.
>
>Does the following agree with your thinking?
>1. A participant (or party) is an organization or business that suppports
>one or more choreographies (e.g. for different ways of doing business with
>partners)
>2. A party can take many roles, e.g buyer, seller, etc
>3. A role can be taken by many parties, e.g many businesses can be a buyer
>4. Choreography definitions are designed to meet some useful "purpose" (e.g.
>place an order)
>5. More than one choreography can exist that meets the same "purpose", e.g.
>there is more than one choreography for placing an order
>6. A choreography involves two or more roles, e.g. a buyer, seller, etc
>7. The roles are depend on the "purpose" of the choreography rather than the
>individual choreography. e.g. you always have a buyer and a seller when
>placing an order irrespective of the actual choreography being used.
>8. Therefore the same roles may be used by more than one choreography.
>
>Thoughts?
>
>David
>
>-----Original Message-----
>From: Assaf Arkin [mailto:arkin@intalio.com]
>Sent: Monday, June 09, 2003 7:33 PM
>To: Burdett, David
>Cc: 'Martin Chapman'; 'Jean-Jacques Dubray'; 'Yaron Y. Goland'; 'WS Chor
>Public'
>Subject: Re: Relationship cardinalities (was ... RE: Requirements:
>Decisio n Po ints Requirement Proposals
>
>
>I assume what you mean by same role is not the fact that both 
>choreographies choose to call it 'buyer', but the fact that in both of 
>them the buyer would be able to act in the same way against the seller. 
>Am I correct?
>
>In that case, would it make more sense to define the buyer's participant 
>and then create two choreographies using that reusable definition?
>
>arkin
>
>
>Burdett, David wrote:
>
>  
>
>>Assaf
>>
>>Here are two example choreographies with the same identical roles.
>>
>>The first does not allow cancelation of the order once it has been
>>    
>>
>accepted.
>  
>
>>Choreography One
>>BUYER             SELLER
>>1. Order ---------->
>>Either ...
>>2.  <------------ Order Response
>>... or ...
>>3.  <------------ Error Response
>>
>>The second does allow cancellation or chances after acceptance
>>
>>Choreography Two
>>BUYER             SELLER
>>1. Order ---------->
>>Either ...
>>2.  <------------ Order Response
>>... or ...
>>3.  <------------ Error Response
>>If Order Response received then, at Buyer's discretion, either ...
>>4. Change Order ---->
>>5.  <------------ Change Order Response
>>... or ...
>>6. Cancel Order ---->
>>7.  <------------ Cancel Order Response
>>If Change Order Response received, and at Buyer's discretion then repeat
>>    
>>
>>from step 4.
>  
>
>>These choreographies are different but the roles (and often the messages)
>>are identical.
>>
>>David
>>
>> 
>>
>>    
>>
Received on Tuesday, 10 June 2003 15:29:50 GMT

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