Re: General semantics

On May 22, 3:09 am, Erwin <e.sm..._at_myonline.be> wrote:
> All database constraints can be formulated in natural language in the
> form "there cannot be any x(,y,z) such that ..."

Algebraically all database constraints can be represented in either of the three equivalent forms:

1. As relational identity.
2. As order constraint (generalized subset relation).
3. As comparison with DUM.

Proof is the following RL equivalences:

• representing order via equality x < y <-> x ^ y = x.
• verse verso x = y <-> x < y & y < x.
• order via comparison with DUM x < y <-> R00 = ((y' ^ x)` ^ x)`.
• comparison with DUM is trivially an equality constraint

show that every order. Received on Mon May 24 2010 - 18:33:09 CEST