RE: [soa-rm] changing shared state to shared view

[Danny Thornton <danny_thornton2@yahoo.com>]

Peter makes an interesting point about views and
state.  I think of a service as containing state
(could be shared state).  I think of a consumer as
having a view or views of a service and a service as
being a provider of views.  Bob observes a book from
the front and it is 7 inches wide and 9 inches tall. 
Jane observes the same book from the side and it is 2
inches wide and 9 inches tall.   The state of the book
remains the same for both views.  If my daughter
changes the state of the book by drawing pretty
pictures on the cover, then the views for Bob and Jane
change.  If the book is morphed into a computing
service, Bob an administrator, and Jane a customer,
there are equivalent computing views for the two views
of the book.  

Applying the above example to changes for lines 141
-144:

[Original 141-144] On the other hand, public actions
result in changes to the state that is shared at least
between those involved in the current execution
context and possibly shared by others.  Real world
effects are, then, couched in terms of changes to this
shared state.

Comment:  Using the airline example, the shared state
change could be the consumer's awareness of the seat
availability or the consumer having reserved a seat. 
The consumer has a view of the seats but does the
consumer have state for the seats?  A reader is likely
to understand the intended meaning of the sentence
without having to ask this question.

[Modified 141-144] On the other hand, public actions
result in changes, some accumulated view of which is
shared at least between those involved in the current
execution context and possibly shared by others. Real
world effects are, then, couched in terms of changes
to this shared view.

Comment: Using the airline example, reserving a seat
on the airline changes the view for current and future
consumers.  The airline service has state for the
seats and provides views of the seats, but does the
airline service itself see views of the seats?    This
takes a little more thought for the reader to
understand.

Danny

--- Peter F Brown <peter@justbrown.net> wrote:

> Ken:
> why "accumulated" in "accumulated view"? I think I
> see where you are going but this sounds a bit
> suspect.
> 
> I'm still not convinced about this choice of word,
> "view":
> 
> Firstly, If two entities share the same view, they
> are standing at the same point and looking at the
> same thing: the point about "shared state" is that
> there are certain characteristics about a service
> interaction that change, including the state of the
> entities engaged in the interaction. They actually
> might have - probably have - different views on
> their...shared state
> 
> Secondly, as a metaphor it doesn't stand up to
> scrutiny and could be confusing: "View" is a
> question of perspective and subjective
> interpretation of an observer, it does not imply any
> change to the reality being viewed. "State" is - or
> at least implies - something more empirical.
> 
> I think shared state is still better...
> 
> Peter
> 
> -----Original Message-----
> From: Ken Laskey [mailto:klaskey@mitre.org] 
> Sent: 09 April 2006 01:55
> To: SOA-RM
> Subject: [soa-rm] changing shared state to shared
> view
> 
> As we came to realize at the end of the call, this
> may be a better means to convey our intent but it
> was not going to be as trivial as a find and
> replace.
> 
> I am including the text of the collected changes
> below and while it looks great in Apple Mail, I have
> no idea what it will look like in Outlook or other
> email clients. I am also attaching a Word document
> with Track Changes.
> 
> Enjoy.
> 
> Ken
> 
> [lines 138-144]
> The purpose of using a capability is to realize one
> or more real world effects. At its core, an
> interaction is an act as opposed to an object and
> the result of an interaction is an effect (or a
> set/series of effects). This effect may be the
> return of information or the change in the state of
> entities (known or unknown) that are involved in the
> interaction. We are careful to distinguish between
> public actions and private actions; private actions
> are inherently unknowable by other parties. On the
> other hand, public actions result in changes, some
> accumulated view of which is shared at least between
> those involved in the current execution context and
> possibly shared by others. Real world effects are,
> then, couched in terms of changes to this shared
> view[KL1].
> [lines 277-282]
> The consequence of invoking a service is a
> realization of one or more real world effects (see
> Section Error! Reference source not found.). These
> effects may include:
> 
> 1.	information returned in response to a request for
> that information,
> 2.	a change to the shared view of defined entities,
> or
> 3.	some combination of (1) and (2).
> 
> Note, the service consumer in (1) does not typically
> know how the information is generated, e.g. whether
> it is extracted from a database or generated
> dynamically; in (2), it does not typically know how
> the changes in the view (or more directly how
> properties of the entities) are effected.
> [lines 464-496]
> Real World Effect
> There is always a particular purpose associated with
> interacting with a service. Conversely, a service
> provider (and consumer) often has a priori
> conditions that apply to its interactions. 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 example, an airline reservation service
> can be used to learn about available flights and
> seating and to eventually book travel the desired
> real world effects being needed information and
> eventually a seat on the right airplane.
> 
> As was discussed in Section 3.1, a real world effect
> can be the response to a request for information or
> the change in the state of some defined entities,
> where the service participants share the combination
> of state information that manifests itself as a
> shared view [and added to Glossary] of the changes.
> In this context, the shared view does not
> necessarily refer to specific state variables being
> saved in physical storage but rather represent
> shared information about the affected entities. So
> in the example of the airline reservation, the
> shared view that there is a seat reserved on a
> particular flight represents a common understanding
> between a future passenger and the airline but the
> details of actual state changes on the part of the
> passenger (e.g. actions required to pay for the
> ticket) or the airline (e.g. that a seat is sold for
> that flight) are not shared by the other.
> 
> 
>
<file://localhost/Users/family/Library/Caches/TemporaryItems/msoclip1/01/clip_image002.png>
> 
> 
> Figure 1 Real World Effect and shared view[KL2] The
> internal actions that service providers and
> consumers perform as a result of participation in
> service interactions are, by definition, private and
> fundamentally unknowable. By unknowable we mean both
> that external parties cannot see others private
> actions and, furthermore, SHOULD NOT have explicit
> knowledge of them. Instead we focus on the set of
> facts shared by the parties the shared view. Actions
> by service providers and consumers lead to
> modifications of this shared view; and a real world
> effect of a service interaction is the accumulation
> of the changes visible through the shared view.
> 
> There is a strong relationship between the shared
> state and the interactions that lead up to that
> state. The elements of the shared state SHOULD be
> inferable from that prior interaction together with
> other context as necessary. In particular, it is not
> required that the state be recorded; although
> without such recording it may become difficult to
> audit the interaction at a subsequent time.[KL3]
> 
> For example, when an airline has confirmed a seat
> for a passenger on a flight this represents a fact
> that both the airline and the passenger share it is
> part of their shared view. Thus the real world
> effect of booking the flight is the modification of
> this shared view the creation of the fact of the
> booking. Flowing from such facts, the passenger, the
> airline, and interested third parties may make
> inferences for example, when the passenger arrives
> at the airport the airline confirms the booking and
> permits the passenger onto the airplane (subject of
> course to the passenger meeting the other
> requirements for traveling).
> 
> For the airline to know that the seat is confirmed
> it will likely require some private action to record
> the reservation. However, a passenger should not
> have to know the details of the airline internal
> procedures; likewise, the airline does not know if
> the reservation was made by the passenger or someone
> acting on the passengers behalf. The passengers and
> the airlines understanding of the reservation is
> independent of how the airline maintains its records
> or the precise individual who initiated the action.
> [between lines 885 and 886]
> Shared view
> The combination of state information that manifests
> itself to service participants as a result of
> interacting with a service.
> 
> [KL1]add to Glossary
> [KL2]need to change figure
> [KL3]Frank Im not sure how to work this in because
> it seems to be requiring visibility beyond the
> shared view. I suggest deleting but I will leave it
> to you to reword.
> 
> 
> 
> 
> 


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