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Subject: Re: [ws-caf-editors] comment question
This is kind of what I was
saying in the AIM conversation Greg and I had. I've always considered that an
activity is used to group related "work" and that the context is the physical
representation of the activity structure.
It's all wordsmithing, but I always found that the
original activity->context relationship was easier to explain to people and
with little confusion. OK, I wasn't at the Paris F2F to witness that confusion,
but then we could always blame a disaffected few and inconsistencies in the
specification.
We can't say anything about this really, unless we
want to get into re-inventing something like WS-Policy. The semantics of the
activity are global, and whether or not a service wants to use/ignore this at a
local level is outside the control of the spec. at the moment.
This is a model/architecture point really. Let's
consider (roughly) the two ways of approaching this:
(i) we define the abstract notion of an activity as
a unit of "work" that is solidified by higher-levels (e.g., made secure work,
transactional work, workflow, ...) Then there is a requirement for services to
be able to identify whether they are participating in that work and, likewise,
for clients to inform services that they are involved in that work and what it
means to be involved in that work. This comes through the context.
or
(ii) we define context as a way of passing
additional information under the covers that is non-functional to the normal
running of the service (e.g., secure, transactional, ...) and used to related
them together somehow. Then we define a notion of an activity that can use the
context if required. But context is irrespective of activity.
Yesterday I wasn't so sure about (ii), but was
prepared to punt on it. However, after spending last night re-reading the
update, I'm more for (i) than (ii). I can see why you might want to go the route
of (ii) if you didn't want to define activities, but I'm not convinced it
actually adds anything and I'm sure it subtracts. The term "activity" is
essentially a short-hand for "grouping of work" or "services that co-operate
somehow" (you get the idea), so we need something like that anyway - you can't
describe context without saying why it's needed and in most cases those terms
will come up. So why not call it an activity? It has mappings into workflow, for
instance, where it's almost a 1-to-1 mapping, transactions, correlation sets,
etc.
Mark.
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