All:
As promised in my last mail, attached is an updated view of the definitions comparison table. I’ve tried to remember to highlight in green the changes and recommendations made compared with the original table sent out.
I propose:
- To keep the 17 January definitions of ‘Action’, ‘Real World Effect’,
- To reintroduce the 28 July definition of ‘Joint Action’ – this will mean rolling back some of the deletions in the 17 January text, where the original use of ‘joint action’ is consistent with this definition;
- To keep the 17 January definition of ‘service activity’ as a generic concept but roll back some of the blanket changes of ‘joint action’ as per previous point – ‘service activity’ is concerned with coordination of all actions within a service; whereas choreography is concerned specifically with joint actions;
- Definition and text related to ‘Shared State’ needs to be revised: at line 909 of 17 January text, we say that “shared state does not imply that the state is accessible to all actors” only that it “may be accessed”. This should correctly belong to a new definition of ‘Public State’ or ‘Shareable State’.
o ‘Public State’ or ‘Shareable State’ : “that part of an entity’s state that is knowable to other actors”; and
o ‘Shared State’ : “the parts of the Public State of an entity accessed by another actor” (modify definition at line 906 of 17 January text); This does imply that shared state can vary in the ‘eye of the beholder’, as different actors may access different parts of the public state – is this correct? And what we intend?
- For ‘Execution Context’ – keep the narrative in section 4.1.2.1.3 which describes the concept adequately without a formal definition
- To modify the text at lines 1068-1069 in the 17 January text to read: “Service is therefore the realisation of such business functionality and accessible through a defined interface.”
In addition, the following dependent concepts would be impacted and are thus asserted or modified:
- ‘Business Transaction’ (use the term ‘activity’ in the definition rather than ‘joint action’ or ‘service activity’)
- ‘Choreography’ – keep existing text but remove definition at lines 2731-2734 (17 Jan pdf). If it is to be defined, use definition in 28 July text (lines 1395-1397: “A choreography is a description of the individual actions to be performed by actors in order to successfully participate in one or more joint actions”)
- We may also want to re-introduce currently deleted text at lines 1238-1246 explaining relevance of choreography and joint action.
- ‘Willingness’: keep text at lines 1250-51 in 17 January draft. Can be quickly ‘converted’ to a formal definition if required (just a ‘callout’ and formatting issue)
- ‘Requirement’ – use 17 January definition
- ‘Objective’ – modify 17 January definition to: “An objective is the real world effect that a participant seeks as a result of using a service” (rather than “..as a result of service activity”)
‘Skill’ – I initially favoured deleting the whole part relating to skill, at lines 798-826, asking what it brings to our draft. I see that we could weave into the text an understanding that (human) skills are relevant in a SOA ecosystem precisely because of the interaction between human and machines; and the need for those humans to act as participants, which implies behaving both as stakeholders in the ecosystem and actors in the system - this does require skill.
Note: ‘Service Method’ is not defined anywhere in the text, either in 28 July or 17 January drafts. If we insist in referring to ‘invocation of service method’ rather than ‘invocation of service’, this would need to be defined. We currently refer to invoking actions against a service. I propose to keep this approach and not open a new problem area.
Best regards,
Peter
Peter F Brown
Independent Consultant
Transforming our Relationships with Information Technologies
Blog pensivepeter.wordpress.com
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