f (s) = {s[V C]} for all s ∈ S1.

Example 33. Consider the same frame as in Example 31. Then consider a VP abstraction, also with  V C = {v}. In this case 
the state space shrinks, since variable u disappears entirely. We get the abstract actions g(a): ∅ ⇒ v and g(b): ∅ ⇒ ∅, but 
no abstract action induces more arcs than its corresponding ground action since the state space shrinks. This is illustrated 
in Fig. 5 (right). Note that g(b) is redundant and can usually be removed.

6.3.  Variable-domain abstraction
A-framework-for-analysing-state-abstraction-metho_2022_Artificial-Intelligen