R (K, A, B, C, X, Y, Z) where: 1. Attribute K is the primary key. 2. Attributes (A B C) exist all the time. 3. Attributes (X Y Z) exist some of the time (but always as a group under the same circumstances). 4. Attributes (X Y Z) require special processing. After denormalising the result is two separate relations, as follows: * R1 (K, A, B, C) * R2 (K, X, Y, Z) where K is also the foreign key to R1