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Re: Use Case Proposal - Supporting the classifier-instance relationship in Web Services

From: Steve Ross-Talbot <steve@enigmatec.net>
Date: Tue, 16 Mar 2004 11:44:40 +0000
Message-Id: <4F4EB95E-773F-11D8-BF84-000393D13C9A@enigmatec.net>
Cc: public-ws-chor@w3.org
To: marcoadr@tin.it

Marco,

We have a new requirements document on the W3C website and wanted to 
check if this covered you requirements in the use case you submitted 
sometime ago.
Could you take a look and let us know.

http://www.w3.org/TR/2004/WD-ws-chor-reqs-20040311/

Best Regards

Steve Ross-Talbot
Chair W3C Web Services Coordination Group
co-Chair W3C Web Services Choreography Working Group

O: +44 207 397 8207
C: +44 7855 268 848

On 16 Sep 2003, at 09:23, marcoadr@tin.it wrote:

>
> I have a Use Case to propose for consideration.
>
> INTRODUCTION
> Composition languages allow the creation a new web service from 
> existent
> ones.
> This define an aggregation/part relationship between the new 
> composition
> and the individual web services that compose it.
> In requirement engineering both the aggregation/part and the 
> classifier/instance
> relationships are fundamental "tools"
> in structuring Problem Analysis and Behavioural requirements.
> The process of turning a problem analysis into a working software 
> solution
> can be simple only if the
> software technology used to implement such solution supports the 
> fundamental
> "tools" of problem analysis.
> Web services arguably lack of a complete support for expressing 
> classifier/instance
> relationship among them.
> With the following use case, I hope to contributes to the support for 
> the
> classifier/instance relationship in Web Services.
>
> Regards
> Marco Adragna
> marco.adragna@kellogg.ox.ac.uk
>
>
>
> 1__INSTANCE-SET USE CASE
>
> 1.1__ACTORS
>
> Parent 		- A Parent is a Web Service allowing users to perform 
> operations
> that relate to
> a set of Instances.
> Typical operations that a Parent COULD support are:
> a)the Addition of a new Instance to the set
> b)the LookUp of an existing instance using business data, primary keys 
> or
> other meaningul information
>
> Instance 	- Each Instance belonging to a given set is a web service
> sharing the same service description (WSDL Interface),
> and maintaining a private state that differentiate it from the others.
>
> Parent and Instance are two roles a Web Service can play in an 
> Instance-Set
> Choreography.
> A Web Service playing the Instance role SHOULD semantically represent 
> an
> Instance Of its Parent Web Service.
>
> User 		- a software system that wish to consume web services that are 
> in
> a relationship of
> classifier/instance with each other.
>
>
>
>
> 1.2__DESCRIPTION
>
> This use case allows providers to express and Users to consume
> two or more web services that are in a classifier/instance relationship
> with each other.
>
> Drawing a parallel with object orientation we could associate:
> Parent 						--> Class
> Instance					--> Object
>
> Parent   WSDL Interface 			--> Class methods  (i.e. Static methods)
> Instance WSDL Interface 			--> Object methods (i.e. Instance methods)
>
> Addition of a new instance to the set 		--> Firing the Constructor 
> method
> of a class
> Parent without support for new instance creation--> Singleton pattern
>
>
>
>
>
>
> 1.3__PRECONDITIONS
>
> The User MUST be aware of the Instance-Set choreography
>
>
>
> 1.4__TRIGGERING EVENT(s)
>
>
> 1.5__POSTCONDITIONS
>
>
> 1.6__FLOW OF EVENTS
>
> 1.6.1__BASIC FLOW
>
> A user might exchange a sequence of messages that logically
> begins with obtaining an identifier of a new Instance from its Parent 
> and
>
> ends either when the private state of that Instance is reclaimed
> or when the User's copy of the Instance
> Identifier is destroyed.
>
>
>
> 1.6.2__ALTERNATE FLOW
>
> A user might exchange a sequence of messages that logically
> begins with obtaining an identifier of an existing Instance from its 
> Parent
> and
> ends either when the Private State of that Instance is reclaimed
> or when the User's copy of the Instance Identifier is destroyed.
> Such existing identifier might be obtained via LookUp operations 
> provided
> by the Parent.
>
>
>
> 1.7__RELATED USE CASES
>
>
> 1.8__NOTES / ISSUES
>
> With "User's copy of the Instance Identifier" we tipically refer to a 
> local
> copy of
> the WSDL document of a remote Instance
> and to any proxy object built using it.
> Other types of instance identifiers could be considered.
>
> The addition of a Factory role should be considered.
>
> No assumption are made on how an instance maintain its private state.
>
> When the "Private State of an Instance is reclaimed" the history of 
> interaction
> of such
> Instance is lost. The Instance return to a state that correspond to a 
> newly
> created instance.
> The private state of that Instance is lost.
> Such event might occour to allow resource pooling at the implementation
> level
> and to limit resource consumption of the provider.
>
> A user might possess an Identifier to an Instance of which the private 
> state
> has been reclaimed.
> A fault condition MUST be generated by messages being sent to such 
> Instance.
>
> Users MUST be able to handle such fault.
> Parent and Instances MUST cooperate in avoiding such fault to ever 
> occour
>
>

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Received on Tuesday, 16 March 2004 06:43:25 GMT

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