Let me begin this by stating that I am not trying to reopen the joint action debate, i.e. the concept of joint action is firmly embedded in the RAF. However, I genuinely do not remember us reaching a final resolution to the questions surrounding Action and Joint Action. I remember asking if joint action was a subtype of action, and if so, what were the other subtypes. Again, I don’t remember if there ever was an answer.
That said, and without prejudice if a previous resolution surfaces, I like the idea of Action subtypes being public and private, and Joint Action is composed of 2..* public actions. This is reflected in the first model below. This disagrees with Michael’s response but here is my logic: Joint Action occurs between Actors and is visible in the ecosystem, i.e. it results in some state change(s) that translate into Real World Effect(s). Any Actor may also engage in private actions as part of responding to a Joint Action, but such private actions are not visible to the ecosystem and, I contend, are outside of the Actor’s scope of interest.
I also like the symmetry with State, and I don’t have strong feelings on whether we introduce public state or just keep shared state. I’ll wait to hear other opinions.
In answer to Peter’s questions:
- Are Service Level RWE and Action Level RWE intended to be the outcomes of, respectively, a Service Action and a Communicative Action? Do we need to align the terms here?
- Are we clear that any RWE caused by a communicative action cannot, by definition, be part of the ‘substantive’ RWE that is delivered by the use of a service? Or would it be better to define RWE as precisely being that ‘soft of’ effect that results only from a service action? In other words, a communicative action will have effects, but not RWEs…
Given the idea of action model and process model as introduced in the RM, any particular action likely results in a change of state and an Action Level RWE. However, we imply that the actions in the Action Model should come together through the Process Model to provide “business level” functionality, i.e. the Service Level RWE. The action level and service level was introduced in the service description discussion because if a service supports a bunch of disjoint actions resulting in diverse RWEs, then description at the service level becomes unwieldy and its use in discovery also gets complicated.
So, as introduced, Action Level RWE and Service Level RWE have nothing to do with Service Action and Communicative Action. Each Action Level RWE will be the result of (possibly) numerous communicative actions, and a combination of Action Level RWE produce the overall Service Level RWE that is documented in the service description.
To my recollection, again subject to better memory on the part of others, service action was questioned but its meaning and use was never resolved.
As for
RWE as both being “a measurable change to the shared state of one or more participants”, but also as a “measurable change in the overall state of the SOA ecosystem”
I think this is an unintended inconsistency.
Other memories welcome.
Ken
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Dr. Kenneth Laskey
MITRE Corporation, M/S H305 phone: 703-983-7934
7515 Colshire Drive fax: 703-983-1379
McLean VA 22102-7508
From: Peter F Brown [mailto:peter@peterfbrown.com]
Sent: Thursday, January 06, 2011 12:30 PM
To: soa-rm-ra@lists.oasis-open.org
Subject: [soa-rm-ra] Action (private action, public action, joint action) and State (private state, shared state, RWE)
Hi:
Firstly, here is the threaded exchange between Ken and myself on the subject of action, private action and joint action:
[Ken] Line 984: Private actions are mentioned in section 3.3. Is it necessary/useful to introduce here? Opacity means private actions, which may be the private part of a joint action, are not publicly visible but are likely essential in realizing real world effect.
[Peter] ??? We don't use the term "private action" anywhere....
[Ken] line 1178-1179 says "...for any given action - whether the action is private or is a joint action...". Also, lines 2231-2232 later say "These operations represent the sequence of actions (often private) a service must perform..." The larger question is what is the relationship between Action and Joint Action. If Joint Action is a type of Action, what (Private Action?) is/are the non-Joint Action types? Note, this has been a long-running issue...
In follow-up to that exchange, I stated:
I think it is incorrect to talk about "private actions, which may be the private part of a joint action". I discussed this with Chris and my view is that an action can be either a private action ('black box' to anyone else even if an RWE can be perceived by others) or a 'public action' (action of a *single* actor, but visible to all). A 'joint action' should be seen as an amalgamation (more formally, an aggregation) of 2 or more public actions. Indeed lines 1178-79 (21 Dec, Clean version) imply that private action and joint action are mutually exclusive. This conclusion came from the thought and question: can you have a joint action without all parties to the action knowing what makes it up?
This would mean we have a model something like, and without any connector between Action and Joint Action:
Models in the current document that show Joint Action as a type of Action would need to change, but without surveying the previous arguments in the TC on this, Ken and I think this approach reasonable.
By analogy, we can look at the issue of State based on the current definitions in the text and this would give us:
We really need an activity or sequence diagram to capture this – as it is a Shared State’s *change* that gives the RWE, something that can’t be easily captured in a class diagram. Note that the cardinality for shared state is 1..* as a single actor’s shared state change can cause an RWE, whereas joint action requires at least two actors’ ‘public actions’ (hence cardinality of 2..*)
I actually argued for the term ‘public state’ rather than ‘shared state’, as our definition of shared state does not imply that the ‘information’ about the state is shared, only that it is shareable. I think that is potentially confusing.
In may be an academic step too far, but could this be an alternative representation:
What we have yet to capture in any diagram is the relationship between joint action, shared state and RWE and also – as raised in s4 – the additional concepts of Service level RWE and Action Level RWE.
Questions first:
- Are Service Level RWE and Action Level RWE intended to be the outcomes of, respectively, a Service Action and a Communicative Action? Do we need to align the terms here?
- Are we clear that any RWE caused by a communicative action cannot, by definition, be part of the ‘substantive’ RWE that is delivered by the use of a service? Or would it be better to define RWE as precisely being that ‘soft of’ effect that results only from a service action? In other words, a communicative action will have effects, but not RWEs…
If we keep the distinct concepts of communicative and service actions, the distinction only makes sense if we consider the former as a sort of ‘support action’ that helps parties prepare for, execute and validate a service action (“are you ready?”, “give me a moment, just checking things…OK, ready now..execute”, “OK, got it”).
We talk of RWE as both being “a measurable change to the shared state of one or more participants”, but also as a “measurable change in the overall state of the SOA ecosystem”. Presumably a communicative action will not have an impact on the ‘overall state’ but rather cause transient effects which have no lasting value – and RWE is all about creating a value for the service participants. Indeed, the RM states that:
‘The service consumer is trying to achieve some result by using the service, as is the service provider. At first sight, such a goal can often be expressed as “trying to get the service to do something”. This is sometimes known as the “real world effect” of using a service’. For me, this is not the same as the outcome of a communicative action. However, the RM goes on to say:
‘a real world effect can be the response to a request for information or the change in the state of some defined entities shared by the service participants. In this context, the shared state does not necessarily refer to specific state variables being saved in physical storage but rather represents shared information about the affected entities.’. This could be understood to favour communicative actions also delivering RWE. My view is that the ‘the request for information’ in the RM example is a service request not an accessory activity.
Comments please – Chris and I will try to come up with some satisfactory wording changes in light of our discussions…
Cheers,
Peter
Peter F Brown
Independent Consultant
Transforming our Relationships with Information Technologies
P.O. Box 49719, Los Angeles, CA 90049, USA
Tel: +1.310.694.2278