In practice, the offset APT A δ can be obtained by prepending the inverse of the path offset, δ −1 , to all of the co-occurrence types in A and then repeatedly applying the reduction operator until no further reductions are possible.
if τ addresses a node in A, then τ addresses a node in A δ iff τ =↓ (δ −1 τ) and τ ∈ R * R * .