Using constraint propagation in MAGPIE: a multi-agent approach

Multimodal presentation planning must solve the constraints imposed by the structure of the discourse. In this paper, we discuss a multi-agent implementation of the design and realization layers of the Standard Reference Model (SRM) for Intelligent Multimedia Presentation Systems (IMMPS), where design constraints for multimodal presentations are distributed over a number of agents. Thus, a constraint propagation mechanism is required so that the distributed constraints can be satisfied cooperatively by these agents.     

Extending a blackboard architecture for approximate processing

Approximate processing is an approach to real-time AI problem-solving systems in domains where there are a range of acceptable answers in terms of certainty, accuracy, and completeness. Such a system needs to evaluate the current situation, make time predictions about the likelihood of achieving current objectives, monitor the processing and pursuit of those objectives, and if necessary, choose new objectives and associated processing strategies that are achievable in the available time. In this approach, the system is performingsatisficing problem-solving, in that it is attempting to generate the best possible solutions within available time and computational resource constraints.Previously published work (Lesser, Pavlin and Durfee 1988) has dealt with this approach to real-time; however, an important aspect was not fully developed: the problem solver must be very flexible in its ability to represent and efficiently implement a variety of processing strategies. Extensions to the blackboard model of problem solving that facilitate approximate processing are demonstrated for the task of knowledge-based signal interpretation. This is accomplished by extending the blackboard model of problem solving to include data, knowledge, and control approximations. With minimal overhead, the problem solver dynamically responds to the current situation by altering its operators and state space abstraction to produce a range of acceptable answers. Initial experiments with this approach show promising results in both providing a range of processing algorithms and in controlling this dynamic system with low overhead.This work was partly supported by the Office of Naval Research under a University Research Initiative grant, number N00014-86-K-0764, NSF-CER contract DCR-8500332, and ONR contract N00014-89-J-1877.     

A blackboard architecture for control

The control problem—which of its potential actions should an AI system perform at each point in the problem-solving process?—is fundamental to all cognitive processes. This paper proposes eight behavioral goals for intelligent control and a ‘blackboard control architecture’ to achieve them. The architecture distinguishes domain and control problems, knowledge, and solutions. It enables AI systems to operate upon their own knowledge and behavior and to adapt to unanticipated problem-solving situations. The paper shows how opm, a blackboard control system for multiple-task planning, exploits these capabilities. It also shows how the architecture would replicate the control behavior of hearsay-ii and hasp. The paper contrasts the blackboard control architecture with three alternatives and shows how it continues an evolutionary progression of control architectures. The paper concludes with a summary of the blackboard control architecture's strengths and weaknesses.     

A blackboard architecture for plastics design

Engineering design is a complex, ill-structured problem involving vast amounts of knowledge that often deal with incomplete, and uncertain, information. The design process typically involves a number of sub-tasks, some of which are amenable to numeric or algorithmic processing (e.g., analysis and optimization); most other sub-tasks require symbolic processing, and are typically solved by expert designers who rely on experiential knowledge used in the form of heuristics. The latter set of sub-tasks were chiefly responsible for creating the symbolic bottleneck that has set back the efforts to automate the design process. However, with the advent of recent AI methodologies we now have techniques for tackling the symbolic bottleneck. Even though some progress has been made in this area with the aid of knowledge-based expert systems, many important questions still remain to be research. In the DESIGNER project we are performing empirical studies that focus on these questions using the plastics design problem as our test bed. We have focused on the preliminary or the base-case design in this domain and have implemented a working prototype called DESIGNER, based on the blackboard architecture. This paper discusses the various aspects of DESIGNER, which is a hybrid, integrated, conferring expert system (HICEX). We are currently extending DESIGNER's capabilities to address the other aspects of the plastics design problem such as part design, plastics processing selection, etc. We are also investigating decentralized communication architectures for integrating multiple experts on the design problem.     

An application of blackboard architecture for the coordination among the security systems

The paper describes the design and implementation of a security architecture for a coordination information system constructed by blackboard architecture (BBA). The need arises for systems to coordinate with one another, to manage diverse attacks across networks and time. The coordination issue is the essential problem since it is beyond the scope of any one intrusion detection system (IDS) to deal with the intrusions. This paper shows a modeling and simulation of network security in which the multiple IDSes and a firewall coordinate by sharing attacker’s information for the effective detection of the intrusion. Another characteristic in the proposed simulation is the composition of a real intrusion by generating non-abstracted intrusion packets and, accordingly, the construction of non-abstracted version of IDS and firewall model components that are closely related to the intrusion packets.     

A middleware architecture for distributed systems management

This paper presents a middleware solution for global management of any kind of distributed system, such as networks of PCs/workstations, clusters or server farms. Our approach lies in an object-oriented software architecture that models all kind of management information using the common information model (CIM) developed by the Distributed Management Task Force (DMTF). The classes and attributes obtained after the modeling process are mapped to a Lightweight Directory Access Protocol (LDAP) repository. This paper discusses the key features of our middleware that allows that any element (physical, logical, device, user or system) can be managed using a network-oriented and topology-independent approach. A representative example of management domain illustrates the procedures followed to build management applications using our middleware architecture.     

Reactive process control using a blackboard architecture

A software architecture to engineer complex process control applications must combine into the same paradigm efficient reactive and real-time functionalities and mechanisms to capture dynamic time-pressured intelligent behaviors, and must provide convenient high level tools to free the programmer from having to think at an unappropriate level of detail. We implement such characteristics into a blackboard framework that builds the basic abstract elements of reactive behavior and the blackboard computational model on top of low level real-time operating system functions. Under this approach, the engineer gets a powerful and flexible high level medium to map a complex system design that requires artificial intelligence techniques, like intelligent monitoring, and reactive planning and execution, with fully support for real-time programming. The paper also reviews other alternatives which have been explored in the past recent years for implementing complex reactive planning and execution systems.     

DIPCS: An interprocess communication architecture for distributed multimedia systems

This paper presents the Distributed InterProcess Communication System (DIPCS) as a framework for managing communication in a distributed multimedia system. Within DIPCS, connection level management is provided through a novel distributed process group model called ADP-Group communication. The ADP-Group paradigm defines a new type of group message passing, calledqos-reliable. Qos-reliable semantics are appropriate to controlling real-time multimedia communication, by allowing a spectrum of performance and reliability specifications to co-exist within one group. DIPCS also provides an abstract programming model of multimedia devices, easing control of a heterogeneous multimedia system. Distributed multimedia applications can be rapidly developed using simple group operation primitives. We show how ADP-Group message delivery semantics can be directly mapped into an efficient Integrated Services Network support policy.Supported by Computational Diagnostics, Inc., and the Benjamin Franklin Fund for the Commonwealth of Pennsylvania.Supported by the Rome Laboratory (RL) of the Air Force Material Command and the Defense Advanced Research Projects Agency (Contract F30602-93-C-0038).     

An architecture for real-time distributed artificial intelligent systems

This paper introduces a new architecture for a real-time distributed artificial intelligence system: DENIS—a Dynamic Embedded Noticeboard Information System. The fundamental idea underlying the architecture draws heavily upon a distributed human system analogy, as seen, for example, in the workplace. The aim of DENIS is to provide a simple, meaningful means by which autonomous intelligent agents can cooperate and coordinate their actions in order to enhance the reliability and effectiveness of a real-time distributed control system. Based on a human paradigm, the architecture inherently allows for the control of an intelligent agent to be taken over by a human operator, yet still to maintain consistency in the distributed system. The key to the thinking in this new approach is to try to model how humans work together, and to implement this in a distributed architecture. One of the main issues raised is that humans owe much of their flexibility to their ability to reason, not only logically, but also in terms of time.     

A software architecture for distributed computer control systems

Distributed computer control systems have a number of potential advantages over centralized systems, especially where the application is itself physically distributed. A computer station can be placed close to the plant being controlled, and a communications network used to enable the stations to communicate to coordinate their actions. However, the software must be carefully designed to exploit the potential advantages of distribution. This paper describes the software architecture of CONIC, a system to support distributed computer control applications. This architecture emphasizes the distinction between the writing of individual software components and the construction and configuration of a system from a set of components. A modular structure is used to separate programming from configuration. Typed entry and exit ports are used to clearly define module interfaces. Ports, analagous to the plugs and sockets of hardware components, permit modules to be interconnected in different ways. On-line modification and extension of the system is supported by permitting the dynamic creation and interconnection of modules. Message passing primitives are provided to permit modules to coordinate and synchronize control actions.     

A blackboard control architecture for model selection and sequencing

Model management systems are computerised systems that facilitate the management of large numbers of decision models used in organizations. Model selection and sequencing in a model management system is the problem of processing a given model base in order to arrive at a sequence of models that can be executed to produce a set of required outputs (goal). Prior solution approaches do not attempt to solve this problem such that the goal is achieved while best meeting the objectives of the user. Instead, research to date has typically provided the first sequence of models which satisfy the goal, without attempting to optimise the objectives of the user. This restricts the applicability of many existing approaches to problems with unique solutions or to situations where users exhibit no preference among the candidate model sequences (i.e. solutions). In many real-world problems, however, multiple solutions may exist and users may prefer a certain solution over the others, based on a variety of criteria such as solution cost, accuracy and so on. In this paper, we present an architecture based on the concept of blackboard control that solves the model selection and sequencing problem while attempting to optimise the objectives of the user. We also discuss the applicability of the proposed approach for solving other problems encountered in the area of model management.     

Object-attribute architecture for design and modeling of distributed automation systems

The application of the object-attribute (OA) architecture of computing environment to implementation of distributed automation systems with computational nodes (computers or PLCs) of different hardware architectures is described. The features of OA modeling of distributed automation tools and the main techniques for modeling, programming, and debugging of such systems are shown.     

Dicaf: a distributed architecture for intelligent transportation

The solution to increasing traffic congestion is not to simply build new roads. Instead, researchers hope to use technology to make more efficient use of the highway network that already exists. Key efforts to date have fallen into two categories. One set of studies has looked at the use of a centralized traffic management center that collects traffic congestion information at a single point and relays it to on-board computers in vehicles or directly to the drivers. Another set of studies has looked at systems that would prescribe the routes for vehicles. The authors describe their Dicaf (distributed scalable architecture for IVHS using a continuous-function congestion measure) system, which envisions a network of distributed, independent traffic management centers that provide congestion and other information to on-board navigation systems in the automobiles themselves. The navigation system uses that information to help drivers avoid slower traffic and thus find the fastest route home or anywhere     

DAMN: a distributed architecture for mobile navigation

An architecture is presented in which distributed task-achieving modules, or behaviours, cooperatively determine a mobile robot's path by voting for each of various possible actions. An arbiter then performs command fusion and selects that action which best satisfies the prioritized goals of the system, as expressed by these votes, without the need to average commands. Command fusion allows multiple goals and constraints to be considered simultaneously. Examples of implemented systems are given, and future research directions in command fusion are discussed.     

e-Automation,an architecture for distributed industrial automation systems

Due to the complexity of modern industrial systems, a conventional automation system is not capable of providing sufficient information management and high-level intelligent approaches, as achieving these functionalities requires the support of comprehensive data management and coordination between system devices and heterogenous information. This paper proposes the concept of e-Automation, in which computer networking and distributed intelligence agent technologies are applied to industrial automation systems, and presents a hardware and software architecture that implements this concept. An open infrastructure based on multi-agent systems is employed in the proposed architecture of e-Automation, which aims to allow the implementation of diverse tasks and to permit greater configurability than can be obtained from a traditional system. To evaluate our proposed e-Automation concept, this paper presents a case study of substation information management which adopts the proposed e-Automation architecture in power system domain.     

Using relaxations to improve search in distributed constraint optimisation

Densely connected distributed constraint optimisation problems (DisCOP) can be difficult to solve optimally, but finding good lower bounds on constraint costs can help to speed up search. We show how good lower bounds can be found by solving relaxed problems obtained by removing inter-agent constraints. We present modifications to the Adopt DisCOP algorithm that allow an arbitrary number of relaxations to be performed prior to solving the original problem. We identify useful relaxations based on the solving structure used by Adopt, and demonstrate that when these relaxations are incorporated as part of the search it can lead to significant performance improvements. In particular, where agents have significant local constraint costs, we achieve over an order of magnitude reduction in messages exchanged between agents. Finally, we identify cases where such relaxation techniques produce less consistent benefits.     

Decentralized architecture for resource management of group-based distributed systems

As the development of hardware and software, large scale, flexible, distributed, secure and coordinated resource sharing has attracted much attention. One of the major challenges is to support distributed group-based resource management, e.g. interest-based organization, with resources/services classifiable. Although there have been some proposals to address this challenge, they share the same weakness of using either severs or super peers to keep global knowledge, and win good search efficiency at the expenses of the system scalability. As a result, such designs can not keep both the search efficiency and system scalability. To that end, this paper proposes a group-based distributed architecture. It organizes the nodes inside the groups by Chord protocol, a classical Peer-to-Peer (P2P) technology and it defines new communication protocol for nodes among different groups but removes servers/super peers for group management. Such a design keeps the resource classifiable property together with good system performance. The main characteristics of this architecture are highlighted by its convenience for group activity analysis, promising scalability, high search efficiency, as well as robustness. The experimental performance results presented in the paper demonstrate the efficiency of the design.     

The InstaGENI initiative: An architecture for distributed systems and advanced programmable networks

In this paper, we describe InstaGENI, a distributed cloud based on programmable networks designed for the GENI Mesoscale deployment and large-scale distributed research projects. The InstaGENI architecture closely integrates a lightweight cluster design with software-defined networking, Hardware-as-a-Service and Containers-as-a-Service, remote monitoring and management, and high-performance inter-site networking. The initial InstaGENI deployment will encompass 34 sites across the United States, interconnected through a specialized GENI backbone network deployed over national, regional and campus research and education networks, with international network extensions to sites across the world.     

FASA: A software architecture and runtime framework for flexible distributed automation systems

Modern automation systems have to cope with large amounts of sensor data to be processed, stricter security requirements, heterogeneous hardware, and an increasing need for flexibility. The challenges for tomorrow’s automation systems need software architectures of today’s real-time controllers to evolve.This article presents FASA, a modern software architecture for next-generation automation systems. FASA provides concepts for scalable, flexible, and platform-independent real-time execution frameworks, which also provide advanced features such as software-based fault tolerance and high degrees of isolation and security. We show that FASA caters for robust execution of time-critical applications even in parallel execution environments such as multi-core processors.We present a reference implementation of FASA that controls a magnetic levitation device. This device is sensitive to any disturbance in its real-time control and thus, provides a suitable validation scenario. Our results show that FASA can sustain its advanced features even in high-speed control scenarios at 1 kHz.