Entailment is Undecidable for Symbolic Heap Separation Logic Formulæ with Non-Established Inductive Rules

Entailment is undecidable in general for Separation (SL) Logic formulæ with inductive definitions, but it has been shown to be decidable [1] if the rules satisfy three conditions, namely progress, connectivity and establishment. We show that entailment latter condition dropped, thus drawing a much clearer frontier (un)decidability.