RE: [soa-rm] Proposed Resolution For Issue #539

["Peter F Brown" <peter@justbrown.net>]

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