Ashley - I don't think it's a matter of "is" here (as in "*is* providing one service or three"). Clearly it's possible to both model and implement a solution either way. What's important is the resulting architecture of the implementation, and in this respect the "3 services" approach offers superior scalability, visibility, reusability, simplicity, to name just a few benefits.
I'll leave the reason why that's so up to others though. Hint; it has something to do with - surprise, surprise - REST. 8-) Mark. On 7/11/06, Ashley at Metamaxim <[EMAIL PROTECTED]> wrote: > > > > > Mark wrote: > > > Well, maybe your TV satellite provider has three services; > > ChannelSelector, MoviePurchaser, and ShowRecorder, and each of those > > services just have the one operation? > > > Here is one way of thinking about the question of the scope of a service > (i.e., whether the TV satellite provider is providing one service with three > operations or three services with one operation). I find this useful, but > there may other approaches: > > Consider the nature and duration of the *dependency* between the consumer > and a specific provider. The idea is that the duration of the service is the > same as the duration of the dependency. > > For example: If I open a Checking Account with Bank X, I am dependent on > Bank X until I close the account. If Bank X goes bust, I am in trouble. If I > decide I do not like Bank X and would rather have my account with Bank Y, I > have to take my money out of Bank X and close the account, and then open a > new account with Bank Y. This transfers my dependency from Bank X to Bank Y. > > What this means is that, if a consumer wants to instantiate a *new service > instance*, he/she/it is free to choose a provider, because there is no > existing dependency that has to be observed. When instantiating an > *operation within a service* the dependency dictates the provider. > > In this sense, the account is a single service instance between me and the > bank, with many operations over time (open, many deposits and withdraws, > close). Similarly, the TV Satellite provider is giving you a single service > with multiple operations. > > > Rgds > Ashley ------------------------ Yahoo! Groups Sponsor --------------------~--> Great things are happening at Yahoo! Groups. See the new email design. http://us.click.yahoo.com/TISQkA/hOaOAA/yQLSAA/NhFolB/TM --------------------------------------------------------------------~-> Yahoo! Groups Links <*> To visit your group on the web, go to: http://groups.yahoo.com/group/service-orientated-architecture/ <*> 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/
