COORDINATING AGENTS - An Analysis of Coordination in Supply-chain Management Tasks (original) (raw)

COORDINATING AGENTS: An analysis of coordination in supply-chain management like tasks}

A multi-agent planning problem consists of a set of activities that need to be planned by several agents. Here, plan coordination methods play an important role, since the independently generated plans by different agents can lead to an infeasible joint solution. We study one particular plan coordination approach, called coordination-by-design, which allows each agent to make its own plan completely independent of the others, while guaranteeing the feasibility of the combined plan of all the agents as a joint solution to the multi-agent planning problem. In this paper, we are interested in a class of multi-agent planning problems that arise in supply-chain management applications. Although the coordination problem in general is Σ p 2-complete, it turns out for this special class, the complexity of coordination checking is polynomial and deciding a minimum coordination set is NP-complete. We develop a polynomial-time approximation algorithm to compute a sufficient coordination set.

Coordination in Multi-Agent Planning with an Application in Logistics

Intelligent Techniques for Planning, 2005

Multi-agent planning comprises planning in an environment with multiple autonomous actors. Techniques for multi-agent planning differ from conventional planning in that planning activities are distributed and the planning autonomy of the agents must be respected. We focus on approaches to coordinate the multi-agent planning process. While usually coordination is intertwined with the planning process, we distinguish a number of separate phases in the planning process to get a clear view on the different role(s) of coordination. In particular, we discuss the pre-planning coordination phase and post-planning coordination phase. In the pre-planning part, we view coordination as the process of managing (sub) task dependencies and we discuss a method that ensures complete planning autonomy by introducing additional (intra-agent) dependencies. In the post-planning part, we will show how agents can improve their plans through the exchange of resources. We present a plan merging algorithm th...

Improving Task-Based Plan Coordination

Lecture Notes in Computer Science, 2011

A multi-agent planning problem consists of a set of activities that need to be planned by several autonomous agents. Here, plan coordination methods play an important role, since independently generated plans by different agents can easily lead to an infeasible joint plan. We study a coordination-by-design approach which allows each agent to make its own plan completely independently of the others, while still guaranteeing the feasibility of the joint plan. The essence of this coordination approach is to determine a minimum number of additional constraints (a minimum coordination set) such that autonomously developed plans satisfying these constraints are always mergeable into an overall feasible plan. It has been shown that such coordination problems are very hard to solve. Therefore, approximation algorithms have been developed to compute a sufficient, but not necessarily minimum coordination set. In this paper, we concentrate on a special class of multi-agent planning problems. These problems arise in several practical applications such as supply chain management and hospital patient treatment. The plan coordination instances in these applications turn out to have a special structure. Using so-called agent dependency graphs, we show that for this special class of problems a better approximation algorithm to compute a sufficient coordination set can be obtained.

Efficient and distributable methods for solving the multiagent plan coordination problem

Multiagent and Grid Systems, 2009

Coordination can be required whenever multiple agents plan to achieve their individual goals independently, but might mutually benefit by coordinating their plans to avoid working at cross purposes or duplicating effort. Although variations of such problems have been studied in the literature, there is as yet no agreement over a general characterization of them. In this paper, we formally define a common coordination problem subclass, which we call the Multiagent Plan Coordination Problem, that is rich enough to represent a wide variety of multiagent coordination problems. We then describe a general framework that

Scheduling the Supply Chain by Teams of Agents

2003

When a supply chain is established supply chain management (SCM) needs supporting tools for the tasks of operative planning, scheduling, and coordination. These tasks have to be performed not only on the level of the enterprises involved but also within their established business entities (e.g. plants, areas, resource groups, resources) in which the high level schedules have to be put into operation. Most approaches of SCM favor a hierarchical coordination of the supply chain together with powerful algorithmic solutions for the mainly predictive scheduling tasks. These approaches are lacking the incorporation of feedback from lower levels and possibilities of reactive scheduling. Thus flexibility and reactivity are main issues to be improved.

Coordinating Non Cooperative Planning Agents: Complexity Results

IEEE/WIC/ACM International Conference on Intelligent Agent Technology, 2005

Whenever independent, non-cooperative actors jointly have to solve a complex task, they need to coordinate their efforts. Typical examples of such task coordination problems are supply chain management, multi-modal transportation and patient-centered health care management. Common elements in such problems are a complex task, i.e., a set of interdependent subtasks, and a set of competitive actors. Solving a task coordination problem first of all requires to solve a task allocation problem (how to assign competitive actors to the subtasks). As a result, each of the actors will receive a set of subtasks to complete and will need to make a plan for this set of tasks. Therefore, also a plan coordination problem has to be solved (how to ensure that a joint plan always can be composed, whatever plan is chosen by the individual actors). The aim of this paper is twofold: first of all to present a general formal framework to study some computational aspects of this non-cooperative coordination problem, and secondly to establish some complexity results and to identify some of the factors that contribute to the complexity of this problem.

Coordinating planning agents for moderately and tightly-coupled tasks

2007

In many task-planning domains, dynamic assemblies of autonomous agents are replacing hierarchical organisations because they promise more agility. In such assemblies, interdependent tasks might be given to different agents that each make a plan for their set of tasks. The feasibility of a joint plan for the total set of tasks, however, is likely to be endangered: Autonomous planning behaviour might result in individually constructed plans that are not jointly feasible. Therefore, (plan) coordination mechanisms have to be introduced to guarantee that even if each individual agent plans its part of the tasks independently from the others, the result will be a feasible joint plan for the complete set of tasks. In previous work we have addressed a coordination mechanism for moderately-coupled tasks, i.e., tasks that are partially ordered by some precedence relation expressing that some task t has to be completed before another task t can be started. Often, however, we have to deal with more complex qualitative temporal relations between tasks. We, therefore, first concentrate on the analysis of qualitative temporal relations between tasks and, using Allen's analysis of temporal interval relations, we show that while some of them can be expressed by precedence relations, others require the addition of a synchronisation relation. We call a set of tasks requiring both precedence relations and synchronisation relations a tightly-coupled set of tasks. The associated problem of coordinating tightly-coupled task systems then concerns the design of a coordination mechanism ensuring the existence of a feasible plan and plan execution process even if each agent is allowed to plan its part of the set of tasks independently from the others. Although we show the associated decision problem to be intractable (Σ p 2-complete) we provide a polynomial-time approximation algorithm that produces a set of additional constraints for each of the agents involved and ensures a feasible joint solution, while the agents keep their planning autonomy.

Cooperative planning in dynamic supply chains

International Journal of Computer Integrated Manufacturing, 2005

This paper describes an order planning system for dynamic supply-chains, addressing the requirements of a make-to-order business environment. A distributed and decentralised information system, based on an architecture of agents and extensively using the internet, was designed and implemented to provide new and more powerful decision support. The system aims at responding to the basic requirements of cooperativeness, integration and configurability. It was developed under the scope of the COOPERATE European Project, and implements the functionality defined in the context of the 'request feasibility studies for the network' business solution.

Framework and Complexity Results for Coordinating Non-cooperative Planning Agents

2006

In multi-agent planning problems agents are requested to jointly solve a complex task consisting of a set of interrelated tasks. Since none of the agents is capable to solve the whole task on its own, usually each of them is assigned to a subset of tasks. If agents are dependent upon each other via interrelated tasks they are assigned to, moderately coupled teams of agents are called for. Such teams solve the task by coordinating during or after planning and revising their plans if necessary. In this paper we show that such complex tasks also can be solved by loosely coupled teams of agents that are able to plan independently, although the computational complexity of the coordination problems involved is high. We also investigate some of the factors influencing this complexity.

A coordination algorithm for Multi-Agent planning

Lecture Notes in Computer Science, 1996

One of the major interests of Multi-Agent Systems (MAS), which are able to handle distributed planning, is coordination. This coordination requires both an adequate plan representation and e cient interacting methods between agents. Interactions are based on information exchange (e.g. data, partial or global plan) and allow agents to update their own plans by including the exchanged information. Coordination generally produces two e ects: it cancels negative interactions (e.g. resource sharing) and it takes advantage of helpful ones (e.g. handling redundant actions). A coordination model should satisfy the following requirements: domain independence, broad covering of interacting situations, operational coordination semantics and natural expression for the designer. This paper presents an adequate framework for the representation and handling of plans in MAS. It then shows how an approach based on a plan representation by means of a partial order model enables the de nition of a coordination algorithm for the possible enrichment of plans.