Re: [soa-rm-ra] OO vs. SOA and what goes into a service

[Rex Brooks <rexb@starbourne.com>]

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
>
>
>------------------------------------------------------------------------------------------
>
>Ken Laskey
>
>MITRE Corporation, M/S H305     phone:  703-983-7934
>
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>
>Attachment converted: Macintosh HD:smime 703.p7s (    /    ) (00366E46)


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Rex Brooks
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