Framework of agent-based intelligence system with two-stage decision-making process for distributed dynamic scheduling
Introduction
Scheduling problems are often found in various business and industrial application areas, for example, in the scheduling of meeting rooms, airline crew assignments, general production, work projects, etc. Although scheduling has played an important role in planning daily routines in many domains, in practice it is still a fairly abstruse matter to handle all types of scheduling problems efficiently. Scheduling is one of the crucial tasks guaranteeing the smooth execution of activities, that is defined as the temporal assignment of activities to resources where a number of goals and constraints have to be considered [20]. In general, it involves two kinds of actions: the creation of schedules of activities over a longer period, which is called predictive scheduling, and adaptations of existing scheduling due to actual events in a scheduling environment, this is called reactive scheduling [22]. Dynamic scheduling (also known as reactive scheduling), which can react to a dynamic environment and adjust as fast as possible, is growing rapidly in importance, and close attention has been paid to it by many researchers and specialists in recent decades [1], [5], [7], [12], [13], [26].
In a highly competitive and changeable environment, the schedule of a multi-contract project [23] can easily encounter various unforeseen circumstances at the project execution phase caused by the influence of various uncertainties. O’Brien indicates that discrepancies between the needed resources for activities and the resources available to subcontractors are a major cause of project changes [18]. Resource discrepancies will occur when the timing of activities is not well matched with the available resources. If subcontractors cannot handle the problem well in time, they may cause delays to the schedule, affecting the schedules and resource allocations of succeeding activities, and even causing the project as a whole to falter or fail.
Another cause of schedule upsets in a distributed project can occur when the traditionally centralized control mechanism of the general contractor ceases to be effective and efficient. In most multi-contract projects, regardless of contract types, 80–90% of tasks commonly are performed by subcontractors, but only 40% of subcontractors are regularly informed by the general contractor when their services will be needed in the project [9]. Although, the general contractor conventionally takes the major responsibility of coordinating all project participants, due to subcontractors’ characteristics of independence, specialization and distribution, many of them do not have contractual relationships with general contractor; accordingly, most subcontractors still have to monitor schedule progress and project difficulties on their own as much as possible [13], [23]. Also, various interface problems can occur at a project execution phase because of the general contractor's lack of specialized expertise, shortage of manpower, and slow responses [2], [9].
Therefore, if project participants were offered the assistance of distributed and real-time system approaches that could automatically coordinate activities and resources, while also encouraging intra-project cooperation based on individual benefits and preferences without the intervention of the general contractor during the project execution phase, then some potential difficulties, such as resource discrepancies, interface problems, inarticulate communications and delays could be predicted and resolved earlier by the subcontractors involved. Such assistance could be important for the success of a project. Several studies have addressed the situation that multiagent systems (MAS), a branch of distributed artificial intelligence, can be satisfactorily applied to such problems [3], [5], [23], [26].
In this paper, a collaborative framework of a distributed agent-based intelligence system with a two-stage decision-making process for dynamic scheduling is addressed. The systems are used to automatically control and resolve the difficulties for project participants in distributed projects, especially focusing on the dynamic scheduling problem solving. Studies of multiagent systems and issues related to this topic are described in Section 2, and the architecture of the agent-based intelligence system for distributed projects is introduced in Section 3. The framework of the two-stage decision-making process performed by the fuzzy decision-making process and the compensatory negotiation process applied to dynamic scheduling is analyzed in Sections 4 Analysis of the two-stage decision-making process for dynamic scheduling, 5 The second-stage decision-making process. The implementation of a prototype system with a case simulation is described in Section 6 to validate the framework, and some conclusions and suggestions for future studies are provided in the final section.
Section snippets
Multiagent systems
Applications of agent technology have been growing rapidly in many domains in recent years. The term “agent” usually refers to an item of hardware or software of the computer system that has the properties of autonomy, social ability, reactivity and pro-activeness. A stronger notion characterizing an agent is the use of mentalistic notions, such as knowledge, belief, intention, and obligation [25]. Multiagent systems represent a new paradigm in analyzing, designing, and solving problems which
Architecture of the agent-based intelligence system
The architecture of the agent-based intelligence system for distributed projects is depicted in Fig. 3. It is an information platform coordinated in real time. The system not only can provide a flexible environment, but also can help all project participants monitor and manage their activities through the assistance of agents. The architecture of the system consists of related logical and physical capability components as shown in the following:
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Naming agent
The naming agent provides supervisory
Operating strategies of activity agents for dynamic scheduling
In the project participant system, each activity agent behaves as if its project participant were performing the activity. The agent possesses the specialized ability of the participant to coordinate with related works in order to keep the activity going smoothly and successfully. It can also cooperate with others based on the individual benefits and preferences characteristic of the participant.
With regard to the problem solving of dynamic scheduling in the framework, if any delay events occur
Framework of the compensatory negotiation model
At the end of the first-stage decision-making process, if there is any PAA whose schedule will be affected by the delay action resulting from the decision made by IAA, then IAA will open negotiation with these PAAs to ensure compensatory agreements for the delay decision. Thus begins the second-stage decision-making process: the compensatory negotiation process. The framework of the compensatory negotiation model for dynamic scheduling is depicted in Fig. 7, which consists of various operating
Implementation and a case example
To validate the feasibility of the framework we have proposed, a prototype system has been developed. We chose Java and JADE [4], [11] for agent programming to implement the prototype, because of the properties of platform independence, a high degree of openness and flexibilities, integrated network ability, FIPA [8] standard compliance and easy extension. Also, we use the case of the distributed project whose contractual relationship and Gantt chart is represented in Fig. 1, Fig. 2,
Conclusion and future works
During a distributed project execution phase, unexpected uncertainties can force the project schedule to change. Resource discrepancies occurring in the execution period of every activity are the major cause of schedule changes. In addition, the traditionally centralized control mechanism of the project being hardly able to control these distributed disturbances, because of the general contractor's lack of specialized expertise, shortage of manpower, and slow response time. Several interface
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