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Summary

The sender wants the receiver to select target agents denoted by a given description and to send an embedded message to them.

Content

A tuple of a descriptor, that is, a referential expression, that denotes the target agents, an ACL communicative act, that is, an ACL message, to be performed to the agents, and a constraint condition for performing the embedded communicative act, for example, the maximum number of agents to be forwarded, etc.

Description

The sending agent informs the recipient that the sender wants the receiver to identify agents that satisfy the given descriptor, and to perform the embedded communicative act to them, that is, the receiver sends the embedded message to them.

On performing the embedded communicative act, the :receiver parameter is set to the denoted agent and the :sender parameter is set to the receiver of the proxy message. If the embedded communicative act contains a :reply-to parameter (for example, in the recruiting case with fipa-recruiting in the :protocol parameter), it should be preserved in the performed message.

In the case of a brokering request, that is, the :protocol parameter is set to fipa-brokering), the brokerage agent (the receiver of the proxy message) must record some parameters, such as :conversation-id, :reply-with, :sender, etc., of the received proxy message to forward back the reply message(s) from the target agents to the corresponding requester agent (the sender of the proxy message).

Formal Model

<i, proxy(j, Ref x d(x), <j, cact>, f)> º

  <i, inform(j, I_i(($y)(B_j(Ref x d(x) = y) Ù Done(<j, cact(y)>, B_jf))))>

    FP : B_iaÙØB_i (Bif_jaÚ Uif_ja)

    RE : B_ja

Where:

  a= I_i(($y) (B_j(Ref x d(x) = y) Ù Done(<j, cact(y)>, B_jf)))

Agent i wants j to perform the embedded communicative act to the denoted agents (y) by Ref x d(x).

Note: <j,cact>in the proxy messageis the ACL communicative act, that is, the ACL message, without a :receiver parameter. Ref xd(x) is one of the referential expressions: ix d(x), any x d(x) or all x d(x).

Two types of proxy can be distinguished. We will call the type of proxy defined above strong, because it is a feasibility precondition of j’s communicative act to y that j satisfies the feasibility preconditions of the proxied communicative act. So, if i proxies an inform of the proposition ψ to y via j, j must believe ψ before it sends the proxied inform message to y.

In addition, we could define weak-proxy, where we do not suppose that j is required to believe ψ. In this case, j cannot directly inform y of ψ, because j does not satisfy the feasibility preconditions of inform.  In this case, j can only inform y that the original sender i has the intention that the inform of ψ should happen. More generally, a weak-proxy can be expressed as an instance of proxy where the action <j,cact(y)> is replaced by <j inform<y, I_i Done(<i, cact(y)>))>.

Example

Agent i requests agent j to do recruiting and request a video-on-demand server to send "SF" programs.

 
(proxy

  :sender i

  :receiver j

  :content

    ((iota ?x

      (registered

        (:agent-description

          (:name ?x)

          (:service-description
            (:service-name video-on-demand)))))

      (request :sender j

        :content

          (action

            (send-program

              (:category "SF")))

        :ontology vod-server-ontology

        :language FIPA-SL

        :protocol fipa-request

        :reply-to i

        :conversation-id request-vod-1)

    true)
  :language FIPA-SL

  :ontology brokerage-agent
  :protocol fipa-recruiting
  :conversation-id vod-brokering-1 …)