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3.4
The Agent Co-ordination Stage
This, the final stage of the Agent Creation process, involves equipping the agent with the co-ordination
protocols and expertise required for social interaction with other agents. This information is entered
through the 'Agent Co-ordination' pane of the Agent Editor.
An Insight into Agent Interactions
But before attempting this stage the developer should have a clear idea of how the agents will interact
in the course of fulfilling their roles. All ZEUS agent interactions are variations on the multi-round
contract-net, [x], which involves one or more Initiators that issue a call for proposals (CFP), and one or
more Respondents that reply. If you are unsure whether a particular role is an Initiator or a Respondent
consult the appropriate role model for guidance.
The key aspects of any agent interaction are the co-ordination protocol and the negotiation strategies.
The co-ordination protocol is an agent conversation model that describes when each party is expected
to communicate, what messages will be exchanged and the effect of receiving particular messages. As
the states assumed by the Initiator and Respondent roles are different, the default co-ordination
protocol is described from both perspectives, as shown in Figure 3.8.
INITIATOR
FAIL
Initialisation
Negotiation
STR ATEG Y
STR ATEG Y
OK
message:
END
At a future time an
ACCEPT or REJECT
message w ill be sent to
the Respondent
CFP
message:
CFP
message:
PROPOSE
Initialisation
STR ATEG Y
decline
Negotiation
consider
END
STR ATEG Y
FAIL
RESPONDENT
Figure 3.8: A state-transition diagram of a typical contract net negotiation
Figure 3.8 also illustrates the relationship between protocols and interaction strategies. At each state
the agent may need to make decisions about how to behave or respond to its current circumstances,
these decisions are decided by strategies. This is best illustrated with an example.
Consider an agent that needs to obtain a resource, because it can not produce it locally it must contact
another agent to supply it. Hence the Initiator begins in the Initialisation state by analysing its
requirements and determining how much it is willing to pay for the resource and how quickly it needs
it. Using the expertise encoded into its tendering strategy it formulates a CFP message containing its
requirements, this is then broadcast to all potentially interested parties and the agent moves into the
Negotiation state to await responses.
ZEUS REALISTION GUIDE
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