What Not How
C J Date's Relational Database Busness Rules
Software Engineering Radically Simplified
Example Rule:
IF S.STATUS < 20 AND S.Snum = SP.Snum
THEN SP.QTY ≤ QTY(500)
Associated checks do not now have to be procedurally encoded in routines:
Create New Shipment
Change Shipment Quantity
Change Supplier Status
Reassign Shipment to Different Supplier
Fewer opportunities for inconsistency and easier to find if occurs.
Services with actions allow us to go further.
@copy 2006 Charles Petrie - permission to reproduce widely with attribution
