0 An idempotent element of a set does not change in value when multiplied by itself.
Every restriction idempotent is restriction inverse to itself, and is therefore extensive.
The projection morphism is well-defined and the minimisation process is idempotent.
This implies that all computed substitutions are idempotent (we will implicitly assume this property in the following).
For example, the following theorem specifies that sort-list is idempotent and is trivial to prove.
With such algorithms, the resulting solution is both unique and idempotent.
We will also use the fact that () is idempotent.
A deflation may or may not be idempotent.
We recall that a closure operator on a partial order is an idempotent, increasing, monotone endofunction.
