Re: Object-relational impedence

JOG wrote:
> I wondered if we might be able to come up with some agreement on what
> object-relational impedence mismatch actually means. I always thought
> the mismatch was centred on the issue that a single object != single
> tuple, but it appears there may be more to it than that.
>
The issue as I've discovered it has to do with the fact OO systems are composed of graphs of data and RDBs are two-dimensional.

What defines an account in an RDB may be composed of multiple tables. An RDB might express multiple account types through multiple tables where OO may reflect it as multiple classes. Attempts to make RDBs function as graphs through mapping tools results in disappointing performance and, in my experience, too much mapping, too much infrastructure, and too much language/paradigm-specific layers. In short, way more code, way more maintenance, and way more job-security for consultants, pundits, and tool providers.

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