Not quite, Ken,
An object usually or typically instantiates a class. It has all the methods it will ever have in its class specification. To add new methods you have to "extend" the class, which means that the new class inherits all of the methods of the class it extends plus whatever new methods you specify.
A SOA service may or may not have a single class it embodies. It may have many classes. The compilation problem Danny cites comes from classes that are composed of a several new classes extending the base class, each in its own turn adding to the total methods involved.
Use a few classes in a service, e.g. a class for adding new contacts with new postal addresses and a class for adding business and personal email addresses; and a couple of classes for different kinds of messages, such as requests and responses, and you get a large set of service components that may belong to a single service such as a reverse 911 message distribution services but are not contained within a single object.
Cheers,
Rex
At 6:05 PM -0500 1/22/08, Ken Laskey wrote:
Is it fair (or at least not too distorted) to say that with OO we define an object and look for what we can do to it (i.e. its methods) while with SOA we identify what we want to do (i.e. business functions) and then, if appropriate, look for objects to do it to?
This gets back to the discussion last October on what actions get bundled together in a service. From an OO perspective, I choose an object and then attach CRUD methods. In SOA, would the CRUD methods individually be things I want to do, each with a describable real world effect (and possibly policies on who can do it and under what conditions), and I define services to carry out those functions?
Are both perspectives/design approaches equally valid? What are the implications for description and discovery?
Ken
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Ken Laskey
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Rex Brooks
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Starbourne Communications Design
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