Ok, I think I got it.

The "conceptual" level intentionally omits the distinguishing attributes for the subtypes. Those will be documented later in the "logical" model. Great!

Will your series follow through with some implementation examples? Maintaining data, implementing UIs , and reporting from designs specifying subtypes has a lot of potential for difficulty when using Sql Server given that the products currently do not provide direct support for subtype implementation.

Therefore the need to maintain procedural code (triggers etc.) to actually maintain data for such structures...

Subtypes are a very useful and effective modeling abstraction, but quite awkward to implement in Sql Server IMHO. If the series can offer some examples for how to overcome Sql Server's inherent implementation hurdles in this area, I think it would add a lot to the discussion.

Thanks,

Ken