"Levels of help, levels of delegation and agent modeling"

Cristiano Castelfranchi, Rino Falcone

Abstract: Cristiano Castelfranchi, Rind FalconeIP-CNR, Group of "Artificial Intelligence, Cognitive Modeling and Interaction"Viale Marx, 15 - 00137 ROMA - ItalyE-mail: {cris, falcone}@pscs2.irmkant.rm.cnr.itIntroductionThe huge majority of DAI and MA, CSCW and negotiationsystems, communication protocols, cooperative softwareagents, etc. are based on the idea that cooperation worksthrough the allocation of some task (or sub-task) of a givenagent (individual or complex) to another agent, via some"request" (offer, proposal, announcement, etc.) meetingsome "commitment" (bid, contract, adoption, etc.). Thiscore constituent of any interactive, negotial, cooperativesystem is not so clear, well founded and systematicallystudied as it could seem. Our claim is that any supportsystem for cooperation and any theory of cooperationrequire an analytic theoly of delegation and adoption. Wewill contribute to an important aspect of this theoo, with aplan-based analysis of delegation.In this paper we try to propose a foundation of the variouslevels of delegation and adoption (help), characterizing theirbasic principles and representations. We try also to identifydifferent agent modeling requirements in relation to thedifferent levels of delegation and/or adoption.We characterize the various levels of the delegation-adoption relation (executive or open; implicit or explicit;on the domain or on the planning; etc.) on the basis of theory of plans, actions and agents.Our claim is that each level of task delegation requiresspecific beliefs (modeling) about both the delegate and thedelegee.Delegation, adoption and their meetingIn this section we supply a general definition of delegation,adoption, and contract, before entering into a more formaland detailed ,analysis of these concepts.Let A and B be two agents. There are two main forms ofdelegation:- A delegates to B a result ? (goal state): i.e. A delegates Bto "bring it about that g", where "to bring it about that g"means to find and execute an action that has g mnong itsrelevant results/effects. Sub-delegation is not excluded.Delegation from A does not require that A knows which isthe action that B has to c,’uxy out: A has only to guess thatthere is such an action.-A delegates to B an action a, i.e. A delegates B toperform (or sub-delegate) We assume that, to delegate an action necessarily impliesto delegate some result of that action [postulate I].Conversely, to delegate a result alwa~,s implies thedelegation of at least one action that produces such a result[postulate II]. Thus, in the following we will consider asthe object of the delegation the couple action/goM x=(a,g)that we call task. With x, we will refer to the action, to itsresulting world state, or to both: this is because a or gmight be implicit or non specified in the request.By definition, a task is a piece/part of a plan (possibly theentire plan); therefore the task has the s,’une hierarchicalstructure of composition and of abstraction of plans.Weak Delegation ("to rely on", "to exploit")Given two agents A and B, and a task x, to assert that Aweakly-d~legates x to B means that:la) (A believes that) isa goal or subgoal of A; thatimplies [1] that:-A believes that (to perform) x is possible;- A believes that (to perform) x is preferable;- A believes that Not (performed) lb) A believes that B is able to perform/bring it about thatx;lc) (A believes that) A has the goal that B performs/bringsit about that x;ld) A believes that B will perform z in time (or A believesthat B is internally committed to perform x in time).le) A has the goal (’relativized’ to ld) of not performing zby itself.In Weak Delegation A exploits B’s activities while Bmight be unaware of this.Weak Adoption ("to take care of")Given two agents A and B, and a task x, to assert that Bweakly-adopts ’r for A means tlmt:2a) B believes that z is a goal or subgoal of A;2b) B believes that B is able to perform/bring it about that2c) (B believes that) B has the goal to perform zfor A; thathnplies that:-B believes that (to perform) ’r is possible;- B believes that (to perform) x is preferable for - B believes that Not (performed) x 2d) B believes that B will perform T in time (or B believesthat B is internally committed to perform x in time).2e) B believes that A will not perform z by itself.Notice that this help can be completely unilateral andspontaneous from B (without any request of A), and/or evenignored by A.Delegation.Adoption (Contract)In Strict Delegation, the delegate knows that the delegee isrelying on him and accepts the task; in Strict Adoption,the helped agent knows about the adoption and accepts it.In other words, Suict Delegation requires Strict Adoption,and vice versa: they are two facets of a unitary socialrelation that we will call "delegation-adoption" or"contract".Given two agents A (the client) and B (the contractor), a task x, to assert that there is a delegation-adoptionrelationship between A and B for x, means that: (la) (2a)(lb) (2b) (lc) (2c) (ld) (2d) (le) (2e). 3a) A and B believe that the other agent believe that x is goal or subgo,’d of A;3b) A and B believe that the other agent believes that B isable to perform/bring it about that x ;3f) A and B believe that A’s goal is that B performs x forA;3g) A and B believe that B is socially committed with A toperform x for A [2];3h) A is socially co~mnitted with B to not perfonning x byhhnself;3i) A and B mutually believe about their reciprocalcommitments.