Catálogo de publicaciones - libros

Emerging pervasive computing technologies such as sensor networks and RFID tags can be embedded in our everyday environment to digitally store and elaborate a variety of information about the surrounding. By having application agents access in a dynamic and wireless way such distributed information, it is possible to enforce a notable degree of context-awareness in applications, increase the capabilities of interacting with the physical world, and eventually give a concrete meaning to the abstract concept of agent situatedness. This paper discusses how both sensor networks and RFID tags can be used to that purpose, outlining the respective advantages and drawbacks of these technologies. Then, to ground the discussion, it presents a multiagent application for physical object tracking, facilitating the finding of “forgot-somewhere” objects in an environment.

This paper analyses the concept of an environment for multi-agent systems from the perspective of a class of manufacturing control systems using stigmergy. The discussion reveals that significant responsibilities can be attributed to the environment as an essential abstraction in MAS. Analysis shows that the environment is well positioned to manage functionalities of multi-agent systems that otherwise would be scattered over the agents, execution platform and communication infrastructure. Importantly, the environment represents a significant contribution handling the complexity of manufacturing control applications and providing a common repository for subsystems originating from different parties.

In situated multi-agent systems (situated MASs), agents are explicitly placed in an environment. A situated agent does not not use long-term planning to decide what action sequence should be executed, but selects actions on the basis of its current position, the world it perceives and limited internal state. Situated agents exploit the environment to coordinate their behavior and to reach a common goal. In a recent project, we applied situated MASs to the control of an automated transportation system that uses automatic guided vehicles (AGVs) to transport loads in a warehouse. In contrast to traditional approaches where the AGVs are controlled by a central server, in this project we model the AGVs as agents in a situated MAS, aiming to improve flexibility and openness. Since the physical environment of AGVs is very restricted, it offers little opportunities for agents to use the environment. We introduce a virtual environment for agents to live in. This virtual environment (1) offers a medium that agents can use to exchange information and coordinate their behavior, and (2) serves as a suitable abstraction to shield low-level physical processing from the AGV agents. Since the only infrastructure available to the AGVs is a wireless network, the virtual environment is necessarily distributed over the AGVs. Synchronization of the state of the virtual environment is provided by ObjectPlaces, a middleware infrastructure that offers support to exchange and share information among nodes in mobile and ad-hoc networks. In this paper, we demonstrate how the environment is used creatively in the design of a MAS solution, helping to manage the complexity of engineering a complex real-world application.

A web site presents an intrinsic graph–like spatial structure composed of pages connected by hyperlinks. This structure may represent an environment in which agents related to visitors of the web site are positioned and moved in order to track their navigation. To consider this structure and to keep track of these movements allows the monitoring of the site and its visitors, in order to support the enhancement of the site itself through forms of adaptivity, but also to introduce new forms of interaction among registered visitors. This paper presents a model supporting the collection of information related to user’s behaviour in a web site, and an application supporting the proposal of hyperlinks based on the history of user’s movement in the web site environment. Moreover the paper briefly describes a system implementing a context-aware form of interaction, supporting the communication among visitors of a web site through the exploitation of its structure.

In the field of multi-agent systems, there has lately been a growing interest on ways in which the environment can better be exploited to coordinate agent behavior and manage complex problems. This paper describes an environment that is able to organize and adapt agent roles as conditions warrant. Roles are adapted using polymorphism as directed by the environment. The design combines strategies from game theory and other biologically inspired models to address fault mitigation in large-scale, real-time, distributed systems. It is implemented on a prototype of the data acquisition system for BTeV, a High Energy Physics experiment consisting of 2500 digital signal processors. Results show environment organization of roles for the lightweight agents embedded within each of the individual processors.

Automatic Guided Vehicles (AGVs) are unmanned vehicles that can transport loads in a warehouse. AGVs are instructed by on-board AGV control software. As multiple AGVs operate in a decentralized manner in the warehouse environment, conflicts may arise. Consequently, it is crucial to test thoroughly whether the AGV control software actually handles the potential conflicts in the appropriate way.

In this paper, we employ a simulated warehouse environment to test the AGV control software. The AGV control software is embedded and activated in the simulated warehouse environment. The simulated warehouse environment provides support for testing by means of (1) representing dynamism in the warehouse environment in an explicit manner, and (2) detecting conflicts of dynamism in an automated way. The approach is illustrated for the case of testing collision avoidance.