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Subject: RE: [soa-rm] Proposed Resolution For Issue #539
good by me. Ken At 09:04 AM 4/26/2006, Peter F Brown wrote: >Ken: >you are right but my mistaken reading may reflect the potential for >misunderstanding of the sentence. Would the following help? > >"On the other hand, public actions result in changes to the state, that >state being shared between at least those involved in the current execution >context and possibly shared by others." > >Peter >-----Original Message----- >From: Ken Laskey [mailto:klaskey@mitre.org] >Sent: 26 April 2006 05:10 >To: peter@justbrown.net >Cc: 'SOA-RM' >Subject: Re: [soa-rm] Proposed Resolution For Issue #539 > >Peter, > >Thanks for the careful read. Only question is your first change of "is" to >"are" -- I think it should remain is because the phrase refers to the state >and not the changes. > >Ken > >On Apr 25, 2006, at 8:36 PM, Peter F Brown wrote: > > > Ken: > I would go along with these formulations. Just a few typo/editorial >changes to your proposed texts, reflected by further changes to your Word >document, as attached > > Peter > > -----Original Message----- > From: Ken Laskey [mailto:klaskey@mitre.org] > Sent: 26 April 2006 00:34 > To: SOA-RM > Subject: [soa-rm] Proposed Resolution For Issue #539 > > Shared state lives! > > The following is the proposed changed text. The attached is a Word >document with Track Changes. > > [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 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. > [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 which the service participants share. In this context, the >shared state 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 >state 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. fund >balances 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/ken/Library/Caches/TemporaryItems/msoclip1/01/clip_i >mage002.png> > > Figure 1 Real World Effect and shared state > > In addition, 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. Actions by service providers and >consumers lead to modifications of this shared state; and a real world >effect of a service interaction is the accumulation of the changes visible >through the shared state. > > 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 state. Thus the real world effect of >booking the flight is the modification of this shared state the creation of >the fact of the booking. Flowing from the shared 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 state > The combination of state information that manifests itself to >service participants as a result of interacting with a service. > > > <proposed issue #539 changes 20060425_PFB.doc> > > >--- >Ken Laskey >MITRE Corporation, M/S H305 phone: 703-983-7934 >7515 Colshire Drive fax: 703-983-1379 >McLean VA 22102-7508 -- --------------------------------------------------------------------------------- / Ken Laskey \ | MITRE Corporation, M/S H305 phone: 703-983-7934 | | 7515 Colshire Drive fax: 703-983-1379 | \ McLean VA 22102-7508 / ----------------------------------------------------------------------------------
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