Question

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

I’ve worked with several projects and all have they used a database centric design and it seems to work fine.

It seems that it’s a new idea flourishing and now it seems fine but the value of it has yeat to be tested or am I wrong?

Answer 1

The idea of an object-relational mismatch comes from the problems that arise when you try and use an object-oriented programming approach backed by a relational database. The problem arises from the fact that object models typically contain hierarchies of objects which need to be shredded into and rebuilt from multiple tables, rather than storing the object as a whole.

However, the argument that normally comes up at this point is that if you haven’t found a problem then it’s your fault because you’re not doing ‘proper’ object-orientation, and that you’ll find the mismatch when you learn to do object-orientation ‘properly’. And we all know that object-orientation is the only ‘proper’ development paradigm.

Oh, wait.

Many systems do not suit being modelled as object-oriented systems. In fact, for things like web applications which tend to have overall low complexity (with localised high complexity) and require high concurrency and scalability, using service-oriented and message-passing techniques can be a better option. When an application is written in this way, you tend to find that there isn’t too much of an object relational mismatch because you don’t use things like lazy loading and complex object hierarchies, and your objects are immutable so they don’t need to be shredded back into the database.

So is there an object-relational mismatch? Yes, if you try and use object-oriented techniques with a relational database. But you can mitigate it by not using object-oriented techniques, if other approaches suit your application better.