[service-orientated-architecture] Re: SOA Reference Architecture

Udi Dahan Mon, 03 Jul 2006 12:05:08 -0700

If we are going to talk about light bulbs, lets turn it up a notch and maybe talk about a movie theater. A movie theater has a number of screening rooms. Each room has light bulbs. When a movie is showing in a room, the light bulbs are dimmed.

In designing a system to manage an automated movie theater, you would probably have a Movie Assignment Service, where someone would plan which movie would show in which room and at what times. They would probably take into account if its opening night and the popularity of the movie. The user would also want to create several alternatives for the same date, several days in advance. At the beginning of each day, a (probably different) user would choose which plan to execute. This plan would be published by the service as the plan to be executed. This plan could also change mid day.

Each screening room would have its own “service” running it. This Screening Room Service would subscribe to the plan to be executed event published by the Movie Assignment Service. It would also control the lights and the projector, curtains, etc for the specific room. When the time would come for it to screen a movie, it would start dimming the lights, open the curtain, start the projector, etc and publish that its state is “now screening” (you wouldn’t want a janitor to start sweeping the floors in the middle). It might also publish the status of each light bulb, but that seems kind of silly. What makes more sense is for it to publish if it has any burnt out light bulbs.

Then you’d have a maintenance “service” which would subscribe to the above events and page janitors and service personnel as needed to handle cleaning and repairs of the screening rooms in such a way as not to interfere with the movie goers.

I believe that this scenario has enough meat to discuss various architectural styles in such a way as to reach conclusions that could be valid for systems in other domains. I think that the light bulb does not. I’d like to hear a REST analysis to compare to this service based one.

Thanks,

Udi Dahan - The Software Simplist

.Net Development Expert & SOA Specialist

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