Supporting cooperation and constraints negotiation under time and resource managers

1. Supporting cooperation and constraints negotiation under time and resource managers Jean-Pierre CAMALOT and Patrick ESQUIROL LAAS-CNRS 7, avenue du Colonel Roche 31077 toulouse cedex email: camalot@laas.fr, esquirol@laas.fr

2. Plan • introduction • network of decision centers • classification of constraints • the decision center model • the interaction model • representation of the decision-making process • conclusion

3. Introduction • distributed decision problem • need of reactivity • autonomy of centers • need to communicate (cooperate, negotiate) more easily • need of support tools • to solve the problem of a center • to communicate with others centers • to represent of the state of one center

4. Network of decision centers • each decision center • corresponds to one or several decision-makers • is characterized by a subset of decision variables • is eventually assisted by software tools • each arc(i,j) means that: • some decisions of agent i are parameters in the constraints of agent j • agent i (resp j) can send to, question or answer to • agent j (resp i) [hug96] : MJ Huguet, J Erschler, G de Terssac and N Lompre. Negotiation based on constraints in cooperation. Computer Supported Cooperative Work (5):267-284

5. B A C Classification of constraints • organizational constraints (network definition) e.g. A must be fixed before tA, B must be fixed after A • model constraints (local model) e.g. B+C > A • protocols or procedural constraints (between 2 centers) e.g. strong commitment: once A is fixed, it cannot be changed

6. The decision center model (1) each local problem is formulated as a CSP Mi = < Xi,Di,Ci > • Xi: decision variables Xi = <Deci, Ini> • Deci : internal decision variables • Ini : incoming decisions variables • Di : domains (one domain for each variable) • Ci: constraints (each constraint restrict the assignments of one or more variables)

7. X2 solution space X1 The decision center model (2) Each agent manages a CSP model. Constraints can be used in various ways such as: • solving • To build a (partial) solution respecting the constraints • constraint propagation • To check consistency of new information • To infer domain tightening on the variables • autonomy evaluation • To evaluate flexibility on external and internal variables

8. The interaction model (1) • cooperation • decision centers regulate their autonomy • two aspects of cooperation : • coordination • time aspects of the cooperation • e.g. causal precedence or time bounds • negotiation • to prevent or to solve conflicts

9. same time different time The interaction model (2) different kinds of cooperative work our approach synchronous interaction asynchronous interaction same place distant synchronous interaction distant asynchronous interaction different place [Foulard98] L’entreprise communicante, Claude Foulard, Hermes 1998

10. The interaction model (3) • different time and indifferent place • asynchronous private messages (e.g. email) • negotiation / renegotiation • decisions are not already taken / decisions are questioned • decision preparation / decision making • no commitment / commitment to honor the result of the process

11. Representation of the decision-making process (1) At time t, several conversations are in progress  2 kinds of decision values : hypothesis commitments decisions communicated or not on which the center does not commit himself decisions communicated on which the center commits himself

12. Representation of the decision-making process (2) initial model commitments current model hypothesis 1 hypothesis 2 M1 M2 hypothesis 3 solving M3 S1

13. Example of autonomy regulation P1 negotiates with RP RP renegotiates with P2 P2 accepts changes RP confirms P1 proposition P1 has gained some autonomy from P2 via RP delivery date 2 delivery date 1 project 1 (P1) project 2 (P2) heavy resource (RH) personnel (RP) starting date of tasks of project 1 starting date of tasks of project 2 amount of personnel for a task

14. Distributed decision support system (1) • Supporting the problem modeling and the problem solving, e.g. : • to determine center autonomy • consistency check • bounds of internals or incoming decisions • sensibility analysis • to evaluate the consequences of some decisions • to determine which constraints to call into question

15. Distributed decision support system (2) • Taking time into consideration, e.g. : • to determine dead lines for the decision-making • to respect the limit date to reply to messages • Supporting communications, e.g. : • to manage mailboxes (selection, ordering, …) • to respect the communications protocols • to determine who to first negotiate with

16. Conclusion (1) • distributed decision problem in a socio-technical context • dynamical environment • modeling both the local problem and its interface with the network and the environment

17. Conclusion (2) • specification of a decision support tool • prototype development • validation on the multi-project management problem (c.f. DIDOM project)

18. desired decisions X2 X1 constraint relaxation