Consider the maximal decompositon of two monadic relations with an IND constraint.
This simple example illustrates an "unrolling" technique of "partially/fully instantiating" predicates to obtain larger numbers of predicates for a different representation of the same information (i.e. a representation that is information equivalent).
The "unrolling" is just a conceptual technique to find parameterised expressions which denote derived relvars which are suited to be the target of updates.
It should not be taken to mean that actual database schemas will be expressed in the unrolled form.
See the S&P example for a more complex/realistic example with INDs.