A Three-Layer Model of Communication
Modeling languages that use only a small number of relations often
seem inadequate for representing communication events. In communication
events, there seem to be too many participants and not enough role
relations:
She gave me the news.
Participants include at least she, the news, me, a
spoken message and sound waves.
A flat model of communication would attempt to hang all of these
participants off role relations of a Communicate event. We have
chosen to model communication events as multiple concurring events at
different levels of concreteness.
At the most abstract level, the example above is communicating information
from speaker to listener:
She communicates news to me.
Two concurring events are also taking place:
She conveys to me a message (in some language).
I hear the sound waves she transmits.
Graphically:

|
Three events: communicating information, conveying a
message and transmitting sound waves. |
More generally, the Communicate event transfers Information
from one Agent to another. In simulation, it is a precondition that
the first Agent already "knows" the Information. And as
a result of simulating the Communicate, the second Agent
will also "know" the Information. Recall that if a precondition in
KM is not known to be true, it will be asserted if it is not inconsistent
with the knowledge base to do so:

|
The basic form of the generic Communicate
event. |
Similarly, the Convey event transfers a Message from one
Agent to another and the Transmit event transfers a
Tangible-Entity playing the role of
Signal from one Place to another. For source and
destination, an Entity is an allowable shorthand for
a Place (the Entity's location):

|
The basic form of the generic Convey and
Transmit events. |
For every Communicate event that transfers Information,
it is assumed that there is a Convey event that transfers a
Message expressing the Information. For every
Convey event that transfers a Message, it is assumed
that there is a Transmit event that transfers a
Tangible-Entity playing the role of Signal embodying the
Message. Not every
Transmit, however, is assumed to be part of some Convey, and
not every Convey is assumed to be part of some Communicate.
So here is a basic representation of the generic Communicate and its
subevents (preconditions and postconditions not shown):

|
The generic Communicate event with subevent
structure (in blue);
Entity nodes are shown gray to distinguish them from
Event nodes. |