Hi > There aren't two forms of communication at this level. Just one.
In terms of the mathematics there are two distinct semantics. The difference is whether the sender and receiver of a message must engage simultaneously in an exchange or not. In service choreography theory, the set of choreographies that can be successfully realized under synchronous communication is different from the set that can realized under asynchronous communication. The former is a superset of the latter. By introducing extra message exchanges and/or locks (which is really the same thing) you can emulate synchronous using asynchronous. But don't let this fool you into thinking that they are the same. Rgds Ashley reamon943 wrote: > > Here's another view. > > At the highest design levels, there is no discussion of sync/async. > There are these items to consider: > > * A sends something to B. > * A can expect a response, or not. > * If a response is expected, there will be a time limit. Millis. > Seconds. Minutes. Hours. Days. Weeks. If a response is not received > within the time limit A will stop waiting/looking/expecting one. What > action A takes after the time limit depends upon the specifics of what > A is doing. > > There aren't two forms of communication at this level. Just one. > > In implementation, one will select the appropriate > technology/technique to address the time constraint. > > The scenario below seems more like a state issue between A and B > rather than a communication concern. But I may be misunderstanding the > example. > > -Rob > > --- In [email protected] > <mailto:service-orientated-architecture%40yahoogroups.com>, > ashley.mcne...@... wrote: > > > > Hi > > > > I haven't followed this thread particularly closely, so this remark may > > not be pertinent. But here goes anyway. > > > > There is a formal difference between synchronous (RPC type) and > > asynchronous communication that can be illustrated as follows: > > > > Suppose that you have two entities A and B, and suppose you require > that: > > > > Either A sends message x to B or B sends message y to A, but not both. > > > > Then you *must* use synchronous communication between A and B. The > > requirement cannot be realized if the communication is asynchronous. > > > > This makes the two forms of communication logically different, > > independently of how they are implemented. > > > > Rgds > > Ashley > > ------------------------------------ Yahoo! Groups Links <*> To visit your group on the web, go to: http://groups.yahoo.com/group/service-orientated-architecture/ <*> Your email settings: Individual Email | Traditional <*> To change settings online go to: http://groups.yahoo.com/group/service-orientated-architecture/join (Yahoo! ID required) <*> To change settings via email: [email protected] [email protected] <*> To unsubscribe from this group, send an email to: [email protected] <*> Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
