A dynamic logic is a Multi-Modal Logic that adds modal operators [ a ] φ delimited-[] 𝑎 𝜑 [a]\varphi and ⟨ a ⟩ φ delimited-⟨⟩ 𝑎 𝜑 \langle a\rangle\varphi for every element a : A : 𝑎 𝐴 a:A of a set of "actions".