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

[Rex Brooks <rexb@starbourne.com>]

I can assure you, from the OASIS WSRP TC viewpoint, re shared-state 
"There Be Dragons." Unless you want to take a ride down the 
whirlpool, it is probably wise to steer away from the area between 
Scylla and Charybdis.

I don't think there is an adequate way to avoid getting very concrete 
once you start making statements about shared state, because you are 
immediately in the realm of session state, method-get v. method-post, 
Asp, Jsp, Php, AJAX, etc. Other than saying that it is possible to 
share state and that it will happen when aggregating services, I 
wouldn't open that door. I don't think you want to skirt the edge of 
using the term "view" in anything other than an utterly abstract 
context. I would actually advise using the term "viewpoint" to move 
it further from "view" which is used in very concrete applications, 
i.e. view:help, view:edit, view:admin, etc.

Cheers,
Rex

At 8:47 AM -0400 4/11/06, Chiusano Joseph wrote:
>Just throwing a potential alternative into the mix:
>
>State alignment (used by BPSS)
>
>Joe
>
>Joseph Chiusano
>Associate
>Booz Allen Hamilton
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>-----Original Message-----
>From: Danny Thornton [mailto:danny_thornton2@yahoo.com]
>Sent: Tuesday, April 11, 2006 5:29 AM
>To: soa-rm@lists.oasis-open.org
>Subject: RE: [soa-rm] changing shared state to shared view
>
>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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-- 
Rex Brooks
President, CEO
Starbourne Communications Design
GeoAddress: 1361-A Addison
Berkeley, CA 94702
Tel: 510-849-2309