Re: [soa-rm-ra] RE: updated service description

On Feb 27, 2007, at 12:07 PM, Duane Nickull wrote:

But if you cannot see the response time of the other service requests for comparison, how can the consumer surmise they got the SLA they are assured of? �Should they really care? �As long as it is within an acceptable amount of time, it shouldn�t matter.

Duane

On 2/27/07 5:42 AM, "Poulin, Michael" <Michael.Poulin@uk.fid-intl.com> wrote:

The "priority over al others" - like silver/gold �user types - may be exposed as a 'response time', which can be easily monitored and measured. Moreover, why a SLA has to contain only run-time characteristics? It may contain a 'change control response time' (in days) as well, right?
The difference between SLA and Service Contract may be viewed as Policy section that cannot be a part of SLA.

- Michael
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From: Duane Nickull �[mailto:[email protected]]
Sent: 26 February 2007 �18:51
To: Ken Laskey; [email protected]
Cc: �[email protected]
Subject: Re: [soa-rm-ra] RE: updated �service description

�
SLA can only encompass externally visible facets of a �services operations, otherwise it is more or less moot. �Why would �someone even contemplate saying �your service request will be treated with �priority over al others� if there is no way to verify or authenticate from an �external standpoint? �SLA�s should really just stick to things like �timeouts, error reporting and other externally visible behaviors.

My �$0.02.

D

On 2/25/07 2:21 PM, "Ken Laskey" �<[email protected]> wrote:

�

Michael,

I started to respond to this hours �ago, then printed out your paper, and finally make it past numerous �distractions (including a unexpected 3 inches of snow to shovel) to finally �collect my thoughts.

On your first point, I think of the service �description as being the executive summary and table of contents. �It �gives you the critical overview and tells you where to find more �details. �So while Interaction Policies & Contracts in the �description may explicitly lay out such things, these are more likely to be �fully defined elsewhere and referenced from the description. �Of �course, one benefit of this is that the policy, for example, becomes �reusable.

As for the personal nature of policy agreements, if it is a �one-time agreement, �I see it residing in the execution context (whose �concrete manifestation is still to be discussed). �If the agreement is �intended to be reused, it should be catalogued somewhere. �The idea of �a general purpose somewhere also needs to be tackled, perhaps (definitely?) �as part of the RA.

I then read your paper and if you went through the �TC emails, you could find discussions touching on but never resolving many �of these issues. �So here are some general questions and some specifics �ones relating to your paper.

- What is a service component? �If �we have a composite service, i.e. one that shows a single interface but is �actually a combination of other services, do you consider the constituent �services to be service components? �In the RM, we distinguish between �the capability and the service that provides access to the capability. ��Is an implementation of the capability also a service component? ��Personally, I think I'd say yes to both where changes to either can affect �the client experience.

- Are "service functions" the same as RM �actions?

- One of my favorites: what belongs in a SLA? �Some �views have it so complete that it basically becomes the service description, �i.e. it describes functionality, constraints, interface details, and the �birthdays of anyone who ever used it. �Personally, I take a more �minimalist approach and think of SLA as being strictly a set of well defined �metrics against which compliance can be measured. �I agree with with �your line that "a SOA service ... is invoked ... when the client is fully �aware of the service behavior and conditions." �(We could quibble over �"fully".) �To accomplish this, I rely on an adequate service �description, of which a metrics-laden SLA is a part. �However, another �part is an indication of how one can obtain metrics collected against the �service. �It is then up to the client to compare the collected metrics �with the SLA and determine fitness for use. �For example, if I have a �service that says I will relieve 80% of world hunger and the metrics show me �only relieving 70%, does my service provide value?

Enough for �now.

Ken

On Feb 25, 2007, at 10:00 AM, �[email protected] wrote:

�

Hi Ken,
�I have two notes to the update �(actually, to the doc as it is with the update):

1) There is an �entity in the Service Description diagram named "Interaction Policies �& Contracts". I think that Contract belongs to another area than �service description because it is 'personalized' based on �consumer/provider agreement. Yes, logically, a Contract is a special type �of description but it would be more comprehensive if we put it into �Interacting with Services Model �section.

2) You have �mentioned <A discussion of how version designation/value should be �impacted by change of version of any of its components (or any �descriptions?) still needs to be discussed.> To me, a version of the �service is one of very important characteristics of the service �description (and, respectively, of the service contract). I would propose �placing version as an entity in the Service Description diagram either �under Identity or at the level of Service Description entity because �version affects Service Reachability, Service Functionality, Interaction �Policies, and Service Interface entities. I have published a few thoughts �about SOA service versioning in SOA-WebServices Journal (http://java.sys-con.com/read/250503.htm �).

- Michael
�

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

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-- �
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Sr. �Technical Evangelist - Adobe Systems, Inc. ��*
Chair - OASIS �SOA Reference Model Technical Committee ��*
Blog: http://technoracle.blogspot.com ��*
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Sr. Technical Evangelist - Adobe Systems, Inc. ��*
Chair - OASIS SOA Reference Model Technical Committee ��*
Blog: http://technoracle.blogspot.com ��*
Music: http://www.mix2r.com/audio/by/artist/duane_nickull*
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Ken Laskey

MITRE Corporation, M/S H305�� phone:��703-983-7934

7515 Colshire Drive� � � � � � � � � � � ��fax:� � � ��703-983-1379

McLean VA 22102-7508

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