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The Object-Relational Impedance Mismatch

November 25, 2010

As described here:

http://en.wikipedia.org/wiki/Object-relational_impedance_mismatch

The origin of the problem is the expectation that everything should have an object description
or equivalent because the object view is general purpose. But in fact there is a more
general purpose paradigm: message passing. A method call on an object is  a special case of passing
a message, which is more tightly bound and less flexible with regard to when the resulting action
occurs and which object or process ultimately handles it.
Message-passing is a natural fit for the way database engines work.
database engines receive
messages (SQL queries) and generate responses from their encapsulated data.
Who cares in their encapsulated data isn’t object-style itself? The
point of  object orientation is encapsulation, and the point of encapsulation is that implementation
details don’t matter.

Encapsulation isnt an end in itself…the end is correctness of data. The ACID objectives are more general and powerful.

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