OASIS Mailing List ArchivesView the OASIS mailing list archive below
or browse/search using MarkMail.


Help: OASIS Mailing Lists Help | MarkMail Help

soa-rm message

[Date Prev] | [Thread Prev] | [Thread Next] | [Date Next] -- [Date Index] | [Thread Index] | [List Home]

Subject: Opaqueness and Transactions

Hi All,

I would like clarification on the following items if possible:


I believe there are degrees of opaqueness. If a service interface allows JAVA classes as a parameter to the actual call, one definitely knows that the service supports JAVA at some level, implying the consumer has some knowledge about the internals of the service (not much but some). The service is not completely opaque.

If the service only allowed XML as incoming data and object constructs, then the parser of choice could be in any language or any other combination of service calls.  I would then say the service is more opaque.

Proposal: There are degrees of opaqueness within the SOA RM and we need to define them.


If a service is a combination service, example, service A is composed of service B and C, are we going to describe the method by which B and C asynchronous responses are delivered to the appropriate reception point within service A? 

Proposal: We need to describe by what method or model we support service composition at run-time.

All comments welcome especially by those who have not said much so far!

Enjoy your face to face,


 -----Original Message-----
From: 	Ken Laskey [mailto:klaskey@mitre.org] 
Sent:	April 20, 2005 4:16 PM
To:	Duane Nickull; SOA-RM
Subject:	Re: [soa-rm] service composition scenarios


I agree with your analysis.  If there is a reason to know details of what 
the service is doing, e.g. a language translation is needed as part of what 
the composite service will do and the user wants to make sure a certain 
class of translation engines is used, then this information should be part 
of the service description/metadata and there may be rules/policy to 
evaluate for the user to make sure the composite server is 
appropriate.  Constructing an orchestrated composite service may be done 
through another service, but such a service will be like any other to the 
RM.  However, the example does indicate there may be a need for specific 
metadata and rules/policy capability and this may or may not go beyond the 
idea of a generic service.  (Or, we may say that an SOA requires certain 
instances of a generic service be present.)


At 03:54 PM 4/20/2005, Duane Nickull wrote:
>Although this may not be part of the core RM, this is probably an 
>interesting discussion to have.  The concept of service composition has 
>been raised a few times on the list.  I wanted to state a few observations 
>about this concept.  Please see attached diagram for details.
>1. Services are opaque by nature.  That means that the service consumer 
>cannot see anything beyond the interface (service interface) it uses.
>If one service is actually aggregating two other services, the service 
>consumer cannot and should not know this.  From a service consumers 
>viewpoint, a service is merely an agent or interface that offer some 
>function(s).  Whether those functions are mapped to a set of classes in 
>some native language or another service is not important or relevant 
>(other than the service metadata stating what invoking the service means 
>or does)
>2. The service function (for service A) is described in the service 
>description specific to that service.  If completing the function depends 
>on two or more serial or parallel paths of execution successfully 
>completing behind the service interface (like calling services B and C) 
>within a certain time frame, that is not relevant to state in the service 
>description for service A.  The service consumer is only concerned with 
>the service's ultimate success or failure.  Mapping the functionality to 
>success and failure is the responsibility of the service provider.
>Do you agree with this?  This supports the notion of opaqueness.
>3. # 1 and # 2 above are mandatory to comply with a services autonomous 
>nature as described in the W3C WSA and subsequent services 
>architectures.  A service alone must determine whether the service 
>succeeds or fails.  If a service consumer can see any specifics behind the 
>service, this violates several of the core principles of SOA.  If 
>visibility beyond the offered service is required, then the service does 
>nor meet the demand of the service consumer.  Accordingly, the service 
>provider and consumer should discuss and re engineer.
>When implementing, more complex patterns of service invocation can be 
>facilitated while keeping these three axioms.  If a transaction sequence 
>is needed, a service interface can offer two services - a put() and a commit().
>Senior Standards Strategist - Adobe Systems, Inc. - http://www.adobe.com
>Vice Chair - UN/CEFACT Bureau Plenary - http://www.unece.org/cefact/
>Adobe Enterprise Developer Resources  - 

   /   Ken 
Laskey                                                                \
  |    MITRE Corporation, M/S H305    phone:  703-983-7934   |
  |    7515 Colshire Drive                    fax:      703-983-1379   |
   \   McLean VA 22102-7508                                              /

*** note: phone number changed 4/15/2005 to 703-983-7934 ***

[Date Prev] | [Thread Prev] | [Thread Next] | [Date Next] -- [Date Index] | [Thread Index] | [List Home]