Summary: Dialogue Concerning the Two Chief Modeling Systems

Jim Weirich, Joe O'Brien, and Chris Nelson acted out a dialog where they built an application to reserve conference rooms.  Very entertaining and novel approach for a tech conference!  I loved it.  But, to the point now - the summary...

So, you want to build something?  

Their are at least two philosophies to fleshing out the model: Traditional object-based modeling and behavior-based modeling.  How are these different?

Object-based data modeling starts with nouns (table names, class names), their sub-properties, and relationships with other nouns.  Behavior-based, asks first what the user's goal is, defines a set of verb-based expressions (methods), and is then followed by the supporting nouns and their relationships derived.  Both have advantages and disadvantages.

Object-based modeling can be brittle when new behaviors are needed.  Behavior-based modeling can lead to object/relational impedance mismatches that are hard to resolve.  

Conclusion

The right answer is... hold on... 

"Think."  

Of course.  Just "think," he says.  In other words, there's no right answer.  

I hate hearing that, even though I know it's true.  So, I pressed Jim later and got this much from him (paraphrased):

Behavior-based modeling is a good fit for application-level data modeling.  Behaviors and their supporting nouns tend to be consistent within an application, regardless of varying ways the data may be persisted.  For system or cross-application data modeling, a more abstract, noun-first (object-based) approach may be better.  This way, the data structure doesn't have to change from application to application.

Object-based data modeling starts with nouns (table names, class names), their sub-properties, and relationships with other nouns.  Behavior-based, asks first what the user's goal is, defines a set of verb-based expressions (methods), and is then followed by the supporting nouns and their relationships derived.  Both have advantages and disadvantages.

Object-based modeling can be brittle when new behaviors are needed.  Behavior-based modeling can lead to object/relational impedance mismatches that are hard to resolve.  

Conclusion

The right answer is... hold on... 

"Think."  

Of course.  Just "think," he says.  In other words, there's no right answer.  

I hate hearing that, even though I know it's true.  So, I pressed Jim later and got this much from him (paraphrased):

Behavior-based modeling is a good fit for application-level data modeling.  Behaviors and their supporting nouns tend to be consistent within an application, regardless of varying ways the data may be persisted.  For system or cross-application data modeling, a more abstract, noun-first (object-based) approach may be better.  This way, the data structure doesn't have to change from application to application.