I'm trying to say this in my paper: "$M$ is a key-value store, where 1) all keys are unique, 2) $k \in M$ means that the $k$ key exists in the store, 3) $M + (k, v)$ is a new store equal to $M$ but the key $k$ is assigned to $v$, 4) $M - k$ is a new store equal to $M$ but without the $k$ key.
Is it possible to omit all this text and just say that "$M$ is something," referring to some well-known definition of such structures?