Distinguishes between adding a new key (init) and updating or referencing a key (get, set, delete).

init is only allowed if the key does not already exist. Get, set and delete are only allowed if the key does already exist.

This is a scalar map in that the keys can only be atomic values, primitives or remotables. Other storeMaps will accept, for example, copyArrays and copyRecords, as keys and look them up based on equality of their contents.