Posting Messages

An index cell ic can be modified to post n messages individually to n output index cells. As a notational convenience, we will write the quadruple as (Ic, W, s', a), where the cardinality of Ic and W must be identical, i.e., Ic = {ic₁,...,ic_n}, W = {y₁,...,y_n}, to indicate that each y_i is posted to each ic_i individually. As a further notational convenience, we will allow Ic and W to be lists. If Ic is of the form [ic,...,ic], this means the messages y_iare all posted to the same ic. If W is of the form [y,...,y], this means the same message y is posted to each ic_i individually.

The above notation enables us to specify the posting of a message y either to an individual ic, or to a group of ic's. In particular, a message can be posted to a certain type of ic, if we do not yet know the identity of the individual ic.

The external environment may also send messages to the active index. In particular, the action sequence may cause the external environment to send messages to some of the index cells, including the index cell that performs the said action sequence. This can be modeled by activating a special ic, similar to the ic₀ described above, to send messages to some of the index cells.