> I think asserting the primacy of a domain model over a relational model - in particular, an OO domain model - is a recipe for pain, especially in a polyglot world.
It's unfortunate that, in common usage, "domain model" basically means "OO domain model". Relational model, one which properly reflects your domain, is most certainly as worthy of that name as an OO one.
We can, of course, debate if simply sharing relational database among multiple applications is good architecture. It very well might not be, due to missing intermediate layer that can absorb schema changes, provide caching, etc. Or due to crappiness of languages used to write stored procedures and databases generally not being great application servers (although PostgreSQL seems to be getting there...)
But it is not because relational model is not a "domain model".
It's unfortunate that, in common usage, "domain model" basically means "OO domain model". Relational model, one which properly reflects your domain, is most certainly as worthy of that name as an OO one.
We can, of course, debate if simply sharing relational database among multiple applications is good architecture. It very well might not be, due to missing intermediate layer that can absorb schema changes, provide caching, etc. Or due to crappiness of languages used to write stored procedures and databases generally not being great application servers (although PostgreSQL seems to be getting there...)
But it is not because relational model is not a "domain model".