Actually, they meant anything you might want control over that affects performance, security, availability, etc without being visible at application level: for example, definitions of indexes, space allocation strategies, recovery journals, etc. I think that definition stands the test of time. Exactly what ANSI SPARC meant by the "conceptual" schema has always been open to debate. The best definition I heard was "a schema written in a language that hasn't been invented yet". As soon as you define a concrete schema language with concrete semantics, it becomes a logical model rather than a conceptual one. Michael Kay Saxonica |