SHAKEN gpd 07280301

The CLib Communication Model

Contents


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.


Information

The Communicate event is special in that the object of the event can be anything that can be known by Agents. We call this intangible entity Information. Information can be communicated, learned, taught, forgotten, lied about, questioned, etc.

Every instance of the Information concept has two important features: its information-content and its truth. The information-content can be any legal KM expression. The truth must be a Truth-Value. If an Agent knows Information it is assumed the the Agent knows its information-content. It is not assumed that the Agent knows its truth.


Information has information-content and truth; An Agent can Know Information without Knowing its truth.


Examples

The following examples are expressed using the generic communication events. For CALO, many specific events common to the office domain will be pre-built. In most cases, only the agent, recipient and information-content will need to be specified.

Example 1

The sysadmin sends out an email that the phones are down.


The recipient has not been stated; the physical (most concrete) layer from the communication model is not shown.

Example 2

Edwin gives a false report.


It is a precondition of the Communicate event that the agent know the Information, so it is assumed that Edwin "knows" the Report;
it is not assumed that he knows the
truth of the Report.

Example 3

Edwin lies.


As with the previous example, it is assumed that Edwin knows the Information;
in this example it is explicit that
Edwin knows the Information is false.