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The applicability of objects architecture for designing real-time reactive operating systems is examined through a model of its elements, their relationships and operations. The requirements of creation, deletion and manipulation of objects in a distributed system with a high degree of fault tolerance are introduced and analyzed. Then, the imposition of time constraints is introduced, and its influence on the objects architecture is analyzed. Relationships with other objects and additional fault tolerance relations are considered. Finally, examples of some solutions to fundamental real-time problems are proposed. Keywords: Systems engineering; Embedding; Computer programming.

The workshop on Large, Distributed, Parallel Architecture, Real-Time Systems was sponsored by the Ballistic Missile Defense Office (BMDO) and the NASA Ames Research Center and hosted at IDA in March 1993. The purpose of the workshop was to obtain expert opinions on the following questions: (1) What is the best design methodology for this class of systems? (2) What is the proper relationship between design theory and scheduling theory? (3) What is the best method for validating this class of systems? and (4) What are the most promising areas where resources might be applied for near-term benefits? Twenty-three experts from academia, government and industry were invited to attend of which seventeen accepted. In total, there were twenty-three participants including sponsors and IDA research staff. The invitees contributed position papers in advance of the workshop and presented talks from transparencies. These position papers and transparencies comprise the contents of the proceedings. The informal discussions that took place at the workshop are summarized in the introductory material by the IDA research staff. The advice, opinions and methods of the participating experts are intended to help BMDO and NASA in the development of their respective software technology planning.

We discuss the application of the Kohn-Nerode-James optimality result of nonlinear systems optimization to the problem of implementing high-safety, high-assurance systems. We state the central problem of feedback control in terms of the most general categories of models (e.g. both logical models and evolution models which are the subject of the field of hybrid systems). We discuss optimal solutions of these nonlinear problems in terms of implementing control programs for a generic architecture suitable for enterprise-wide coordination and control. Finally we provide definitions of enterprise-wide, closed-loop control problems for several large-scale systems using this architecture and discuss synchronization with enterprise coordination processes. We summarize results for a reference architecture being demonstrated for the Department of Defense. (AN)

Software architecture, configuration management, and configurable distributed systems are three areas of research that until now have evolved separately. Contributions in each field have focused on their respective area of concern. However, as solutions in the three fields tend to center around some notion of a system model, it is worthwhile to investigate their relationship in detail. In particular, the large amount of overlap among the system models developed in each area, combined with the complementary nature of the differences among them, suggests that an approach based on a common system model is viable. In this paper, we illustrate the benefits of using such a unified system model, identify the commonalities and differences among the existing system models, and present some of our initial experiments that we believe will lead to the development of a single system model that is usable in all three fields.

The Space Station Axiomatic Fault Isolating Expert Systems (SAFTIES) system deals with the hierarchical distribution of control and knowledge among independent expert systems doing fault isolation and scheduling of Space Station subsystems. On its lower level, fault isolation is performed on individual subsystems. These fault isolation expert systems contain knowledge about the performance requirements of their particular subsystem and corrective procedures which may be involved in repsonse to certain performance errors. They can control the functions of equipment in their system and coordinate system task schedules. On a higher level, the Executive contains knowledge of all resources, task schedules for all systems, and the relative priority of all resources and tasks. The executive can override any subsystem task schedule in order to resolve use conflicts or resolve errors that require resources from multiple subsystems. Interprocessor communication is implemented using the SAFTIES Communications Interface (SCI). The SCI is an application layer protocol which supports the SAFTIES distributed multi-level architecture.

The AI Bus architecture is layered, distributed object oriented framework developed to support the requirements of advanced technology programs for an order of magnitude improvement in software costs. The consequent need for highly autonomous computer systems, adaptable to new technology advances over a long lifespan, led to the design of an open architecture and toolbox for building large scale, robust, production quality systems. The AI Bus accommodates a mix of knowledge based and conventional components, running on heterogeneous, distributed real world and testbed environment. The concepts and design is described of the AI Bus architecture and its current implementation status as a Unix C++ library or reusable objects. Each high level semiautonomous agent process consists of a number of knowledge sources together with interagent communication mechanisms based on shared blackboards and message passing acquaintances. Standard interfaces and protocols are followed for combining and validating subsystems. Dynamic probes or demons provide an event driven means for providing active objects with shared access to resources, and each other, while not violating their security.

The Clouds kernel design was through several design phases and is nearly complete. The object manager, the process manager, the storage manager, the communications manager, and the actions manager are examined.

The Clouds project is well underway to its goal of building a unified distributed operating system supporting the object model. The operating system design uses the object concept of structuring software at all levels of the system. The basic operating system was developed and work is under progress to build a usable system.

The Clouds project is well underway to its goal of building a unified distributed operating system supporting the object model. The operating system design uses the object concept of structuring software at all levels of the system. The basic operating system was developed and work is under progress to build a usable system.

The Clouds project is well underway to its goal of building a unified distributed operating system supporting the object model. The operating system design uses the object concept of structuring software at all levels of the system. The basic operating system was developed and work is under progress to build a usable system.

The Clouds project is well underway to its goal of building a unified distributed operating system supporting the object model. The operating system design uses the object concept of structuring software at all levels of the system. The basic operating system was developed and work is under progress to build a usable system.

The Clouds project is well underway to its goal of building a unified distributed operating system supporting the object model. The operating system design uses the object concept of structuring software at all levels of the system. The basic operating system was developed and work is under progress to build a usable system.

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Real time embedded systems have particularly strict requirements on accuracy, safety and reliability. A central question in the design of such systems is how to support concurrent processing without adversely affecting the timing requirements of the system. Concurrent processing is essential because the only way to successfully meet some tight real time constraints is to use multiple processors. This thesis focuses on the distributed scheduling problem. It proposes a distributed scheduling algorithm to allocate and schedule a set of tasks onto a collection of processors linked by a network. It further proposes a distributed software architecture for CAPS (Computer Aided Prototyping System) generated prototypes based on GLADE (GNAT Library for Ada Distributed Execution). The new distributed CAPS architecture is applied to several prototype examples. The results show that it is possible to build distributed real time embedded systems under the distributed scheduling model, where sets of tasks run independently on each processor, using GLADE.

Real time embedded systems have particularly strict requirements on accuracy, safety and reliability. A central question in the design of such systems is how to support concurrent processing without adversely affecting the timing requirements of the system. Concurrent processing is essential because the only way to successfully meet some tight real time constraints is to use multiple processors. This thesis focuses on the distributed scheduling problem. It proposes a distributed scheduling algorithm to allocate and schedule a set of tasks onto a collection of processors linked by a network. It further proposes a distributed software architecture for CAPS (Computer Aided Prototyping System) generated prototypes based on GLADE (GNAT Library for Ada Distributed Execution). The new distributed CAPS architecture is applied to several prototype examples. The results show that it is possible to build distributed real time embedded systems under the distributed scheduling model, where sets of tasks run independently on each processor, using GLADE.

Monitoring is an essential process to observe and improve the reliability and the performance of large-scale distributed (LSD) systems. In an LSD environment, a large number of events is generated by the system components during its execution or interaction with external objects (e.g. users or processes). Monitoring such events is necessary for observing the run-time behavior of LSD systems and providing status information required for debugging, tuning and managing such applications. However, correlated events are generated concurrently and could be distributed in various locations in the applications environment which complicates the management decisions process and thereby makes monitoring LSD systems an intricate task. We propose a scalable high-performance monitoring architecture for LSD systems to detect and classify interesting local and global events and disseminate the monitoring information to the corresponding end- points management applications such as debugging and reactive control tools to improve the application performance and reliability. A large volume of events may be generated due to the extensive demands of the monitoring applications and the high interaction of LSD systems. The monitoring architecture employs a high-performance event filtering mechanism to efficiently process the large volume of event traffic generated by LSD systems and minimize the intrusiveness of the monitoring process by reducing the event traffic flow in the system and distributing the monitoring computation. Our architecture also supports dynamic and flexible reconfiguration of the monitoring mechanism via its Instrumentation and subscription components. As a case study, we show how our monitoring architecture can be utilized to improve the reliability and the performance of the Interactive Remote Instruction (IRI) system which is a large-scale distributed system for collaborative distance learning. The filtering mechanism represents an Intrinsic component integrated with the monitoring architecture to reduce the volume of event traffic flow in the system, and thereby reduce the intrusiveness of the monitoring process. We are developing an event filtering architecture to efficiently process the large volume of event traffic generated by LSD systems (such as distributed interactive applications). This filtering architecture is used to monitor collaborative distance learning application for obtaining debugging and feedback information. Our architecture supports the dynamic (re)configuration and optimization of event filters in large-scale distributed systems. Our work represents a major contribution by (1) survey and evaluating existing event filtering mechanisms In supporting monitoring LSD systems and (2) devising an integrated scalable high- performance architecture of event filtering that spans several kev application domains, presenting techniques to improve the functionality, performance and scalability. This paper describes the primary characteristics and challenges of developing high-performance event filtering for monitoring LSD systems. We survey existing event filtering mechanisms and explain key characteristics for each technique. In addition, we discuss limitations with existing event filtering mechanisms and outline how our architecture will improve key aspects of event filtering.

The Marshall Space Flight Center (MSFC) Ground Systems Department (GSD) recently undertook an architecture change in the product line that serves the ISS program. As a result, the architecture tradeoffs between data system product lines that serve remote users versus those that serve control center flight control teams were explored extensively. This paper describes the resulting architecture that will be used in the International Space Station (ISS) payloads program, and the resulting functional breakdown of the products that support this architecture. It also describes the lessons learned from the path that was followed, as a migration of products cause the need to reevaluate the allocation of functions across the architecture. The result is a set of innovative ground system solutions that is scalable so it can support facilities of wide-ranging sizes, from a small site up to large control centers. Effective use of system automation, custom components, design optimization for data management, data storage, data transmissions, and advanced local and wide area networking architectures, plus the effective use of Commercial-Off-The-Shelf (COTS) products, provides flexible Remote Ground System options that can be tailored to the needs of each user. This paper offers a description of the efficiency and effectiveness of the Ground Systems architectural options that have been implemented, and includes successful implementation examples and lessons learned.

The Marshall Space Flight Center (MSFC) Ground Systems Department (GSD) recently undertook an architecture change in the product line that serves the ISS program. As a result, the architecture tradeoffs between data system product lines that serve remote users versus those that serve control center flight control teams were explored extensively. This paper describes the resulting architecture that will be used in the International Space Station (ISS) payloads program, and the resulting functional breakdown of the products that support this architecture. It also describes the lessons learned from the path that was followed, as a migration of products cause the need to reevaluate the allocation of functions across the architecture. The result is a set of innovative ground system solutions that is scalable so it can support facilities of wide-ranging sizes, from a small site up to large control centers. Effective use of system automation, custom components, design optimization for data management, data storage, data transmissions, and advanced local and wide area networking architectures, plus the effective use of Commercial-Off-The-Shelf (COTS) products, provides flexible Remote Ground System options that can be tailored to the needs of each user. This paper offers a description of the efficiency and effectiveness of the Ground Systems architectural options that have been implemented, and includes successful implementation examples and lessons learned.

The Marshall Space Flight Center (MSFC) Ground Systems Department (GSD) recently undertook an architecture change in the product line that serves the ISS program. As a result, the architecture tradeoffs between data system product lines that serve remote users versus those that serve control center flight control teams were explored extensively. This paper describes the resulting architecture that will be used in the International Space Station (ISS) payloads program, and the resulting functional breakdown of the products that support this architecture. It also describes the lessons learned from the path that was followed, as a migration of products cause the need to reevaluate the allocation of functions across the architecture. The result is a set of innovative ground system solutions that is scalable so it can support facilities of wide-ranging sizes, from a small site up to large control centers. Effective use of system automation, custom components, design optimization for data management, data storage, data transmissions, and advanced local and wide area networking architectures, plus the effective use of Commercial-Off-The-Shelf (COTS) products, provides flexible Remote Ground System options that can be tailored to the needs of each user. This paper offers a description of the efficiency and effectiveness of the Ground Systems architectural options that have been implemented, and includes successful implementation examples and lessons learned.

With the increase of the number of vehicles on the road, several traffic congestion problems arise in the big city, and this has a negative impact on the economy, environment and citizens. The time spent looking for a parking space and the traffic generated contributes to mobility and traffic management problems. Hence the need for smart parking management to help drivers to find vacant spaces in a car park in a shorter time. Today, researchers are considering scenarios in which a large amount of services can be offered and used by drivers and authorities to improve the management of the city's car parks and standards of quality of life. Based on literature on smart parking management system (SPMS), we have established the most important services needed such as reservation, orientation, synchronization, and security. The dynamic distributed and open aspect of the problem led us to adopt a multi-agent modeling to ensure continuous evolution and flexibility of the management system. In this conceptual paper, we propose to structure those services on a multi-agent system (MAS) that covers the whole functions of a distributed SPMS. Each service is provided as an autonomous agent, able to communicate and collaborate with the others to propose optimized parking space to customers.

The primary focus of this report is on system architectures and protocols for building fault-tolerant distributed systems. It addresses algorithms and protocols in four different areas: fault-diagnosis, error recovery in replicated systems, error recovery based on self-stabilization, and the use of masking redundancy in replicated systems using agreement protocols. This report is a collection of six technical papers that present the results obtained in this area. The first paper describes a system architecture for building resilient processes using replication and check pointing. It describes the protocols for process replication management. The second paper presents an agreement protocol which provides the same view of the computation state to each correctly functioning copy of the process. The third paper presents a protocol for self-stabilization in binary trees. This protocol is a generalization of one of Dijkstra's protocols and for normal operations is sufficient to guarantee recovery from any erroneous state. The fourth paper presents a protocol for detecting the termination of a set of cooperating communicating processes. The last two papers address the problems related to fault-diagnosis in interconnected systems. The first presents a survey of the various fault- diagnosis algorithms based on the model proposed by Preparata, Metze & Chen (PMC Model). The second presents some results in direction of designing more efficient fault-diagnosis algorithms. Keywords: Computer architecture; Fault tolerant computing.

This paper introduces a framework for studying the interactions of autonomous system components and the design of the connectivity structure in Systems of Systems (SoSs). This framework, which uses complex network models, is also used to study the connectivity structure's impact on resource management. We discuss resource sharing as a mechanism that adds a level of flexibility to distributed systems and describe the connectivity structures that enhance components' access to the resources available within the system. The framework introduced in this paper explicitly incorporates costs of connection and the benefits that are received by direct and indirect access to resources and provides measures of the optimality of connectivity structures. We discuss central and a distributed schemes that, respectively, represent systems in which a central planner determines the connectivity structure and systems in which distributed components are allowed to add and sever connections to improve their own resource access. Furthermore, we identify optimal connectivity structures for systems with various heterogeneity conditions.

We consider a distributed antenna system where $L$ antenna terminals (ATs) are connected to a Central Processor (CP) via digital error-free links of finite capacity $R_0$, and serve $L$ user terminals (UTs). This system model has been widely investigated both for the uplink and the downlink, which are instances of the general multiple-access relay and broadcast relay networks. In this work we focus on the downlink, and propose a novel downlink precoding scheme nicknamed "Reverse Quantized Compute and Forward" (RQCoF). For this scheme we obtain achievable rates and compare with the state of the art available in the literature. We also provide simulation results for a realistic network with fading and pathloss with $K > L$ UTs, and show that channel-based user selection produces large benefits and essentially removes the problem of rank deficiency in the system matrix.

Ubiquitous sensing devices frequently disseminate data among them. The use of a distributed event-based system that decouples publishers from subscribers arises as an ideal candidate to implement the dissemination process. In this paper, we present a network architecture that merges the network and overlay layers of typical structured event-based systems. Directional random walks are used for the construction of this merged layer. Our strategy avoids using a specific network protocol that provides point-to-point communication. This implies that the topology of the network is not maintained, so that nodes not involved in the system are able to save energy and computing resources. We evaluate the performance of the overlay layer using directional random walks and pure random walks for its construction. Our results show that directional random walks are more efficient because: (1) they use less nodes of the network for the establishment of the active path of the overlay layer and (2) they have a more reliable performance. Furthermore, as the number of nodes in the network increases, so do the number of nodes in the active path of the overlay layer for the same number of publishers and subscribers. Finally, we discard any correlation between the number of nodes that form the overlay layer and the maximum Euclidean distance traversed by the walkers.

The use of artificial intelligence (AI) techniques for pilot aiding in real-time (DoD Pilot Associate--PA) introduces some seemingly intractable problems. Most algorithms which will be used in a PA are search intensive with exponential-order-time-co mplexities. The thesis outlines the problem and explores the possibility of using parallel processing for minimizing the computational costs. Methods for, and results from, distributing data and functions among many processors are presented. An extension to the blackboard structure used in many AI systems called a 'virtual blackboard' is introduced. The results and techniques are bundled into a prototype distributed data-flow constraint-network application system called DDAFCON. DDAFCON is discussed, and a flight-planning application is presented using DDAFCON. The results are discussed. It is shown that the maximum speedup due to parallel processing is bounded by the number of processors which a problem solution can accept. The thesis concludes that generalized AI structures and reasoning paradigms (specifically, 'deep models'), although seemingly required for the performance level desired for applications such as the PA may not be realizable for many real-time applications. A change in emphasis for developing real-time AI systems is suggested.

Adaptive Distributed Control System (ADCS) architectures have been developing rapidly in all fields to provide for optimal control, prognosis and safety-critical systems. Concepts such as controller decentralization and smart sensor/actuators have been studied by both government agencies and industry. Distributed control is potentially an enabling technology for advanced intelligent propulsion system concepts and is one of the few control approaches that is able to provide improved component and control system prognostics, as well as fault-tolerance. ADCS architectures offer the potential of enhanced reliability and the ability to maintain optimal performance when the propulsion system degrades. An ADCS will reduce the impact of hardware and software obsolescence. Control system weight will be reduced by replacing heavy harness assemblies and FADECs, with distributed processing elements interconnected. This paper reviews current activities that may lead to the development of standards for distributed, safety-critical and supportable intelligent propulsion systems of the future.

The objective of the High Performance Distributed Systems Architecture (HPDSA) project are to integrate very high bandwidth networks with heterogeneous computer architectures (including parallel and specialized processors) and support multiple programming models with this system. The driving forces for this project are user demands for high- performance computing coupled with the availability of gigabit and high bandwidth networking. Command and control applications are increasingly requiring the capabilities of both specialized processors and supercomputer-class machines. These resources are often concentrated at computer centers while the data sources and users of these systems are geographically distributed. By linking users, data sources, and systems together with high-speed networks and distributed operating systems, we can substantially improve the quality of command and control information and provide that information to more people. A high-performance distributed operating system must satisfy a number of design goals to accomplish our architectural objectives. Foremost, it must be capable of accommodating a wide variety of computers, networks and programming languages.

The objective of the High Performance Distributed Systems Architecture (HPDSA) project are to integrate very high bandwidth networks with heterogeneous computer architectures (including parallel and specialized processors) and support multiple programming models with this system. The driving forces for this project are user demands for high- performance computing coupled with the availability of gigabit and high bandwidth networking. Command and control applications are increasingly requiring the capabilities of both specialized processors and supercomputer-class machines. These resources are often concentrated at computer centers while the data sources and users of these systems are geographically distributed. By linking users, data sources, and systems together with high-speed networks and distributed operating systems, we can substantially improve the quality of command and control information and provide that information to more people. A high-performance distributed operating system must satisfy a number of design goals to accomplish our architectural objectives. Foremost, it must be capable of accommodating a wide variety of computers, networks and programming languages.

The objective of the High Performance Distributed Systems Architecture (HPDSA) project are to integrate very high bandwidth networks with heterogeneous computer architectures (including parallel and specialized processors) and support multiple programming models with this system. The driving forces for this project are user demands for high- performance computing coupled with the availability of gigabit and high bandwidth networking. Command and control applications are increasingly requiring the capabilities of both specialized processors and supercomputer-class machines. These resources are often concentrated at computer centers while the data sources and users of these systems are geographically distributed. By linking users, data sources, and systems together with high-speed networks and distributed operating systems, we can substantially improve the quality of command and control information and provide that information to more people. A high-performance distributed operating system must satisfy a number of design goals to accomplish our architectural objectives. Foremost, it must be capable of accommodating a wide variety of computers, networks and programming languages.

Real time embedded systems have particularly strict requirements on accuracy, safety and reliability. A central question in the design of such systems is how to support concurrent processing without adversely affecting the timing requirements of the system. Concurrent processing is essential because the only way to successfully meet some tight real time constraints is to use multiple processors. This thesis focuses on the distributed scheduling problem. It proposes a distributed scheduling algorithm to allocate and schedule a set of tasks onto a collection of processors linked by a network. It further proposes a distributed software architecture for CAPS (Computer Aided Prototyping System) generated prototypes based on GLADE (GNAT Library for Ada Distributed Execution) . The new distributed CAPS architecture is applied to several prototype examples. The results show that it is possible to build distributed real time embedded systems under the distributed scheduling model, where sets of tasks run independently on each processor, using GLADE.

Real time embedded systems have particularly strict requirements on accuracy, safety and reliability. A central question in the design of such systems is how to support concurrent processing without adversely affecting the timing requirements of the system. Concurrent processing is essential because the only way to successfully meet some tight real time constraints is to use multiple processors. This thesis focuses on the distributed scheduling problem. It proposes a distributed scheduling algorithm to allocate and schedule a set of tasks onto a collection of processors linked by a network. It further proposes a distributed software architecture for CAPS (Computer Aided Prototyping System) generated prototypes based on GLADE (GNAT Library for Ada Distributed Execution) . The new distributed CAPS architecture is applied to several prototype examples. The results show that it is possible to build distributed real time embedded systems under the distributed scheduling model, where sets of tasks run independently on each processor, using GLADE.

The ObjectAgent system is being developed to create an agent-based software architecture for autonomous distributed systems. Agents are used to implement all of the software functionality and communicate through simplified natural language messages. Decision-making and fault detection and recovery capabilities are built-in at all levels. During the first phase of development, ObjectAgent was prototyped in Matlab. A complete, GUI-based environment was developed for the creation, simulation, and analysis of multi-agent, multi-satellite systems. Collision avoidance and reconfiguration simulations were performed for a cluster of four satellites.

The ObjectAgent system is being developed to create an agent-based software architecture for autonomous distributed systems. Agents are used to implement all of the software functionality and communicate through simplified natural language messages. Decision-making and fault detection and recovery capabilities are built-in at all levels. During the first phase of development, ObjectAgent was prototyped in Matlab. A complete, GUI-based environment was developed for the creation, simulation, and analysis of multi-agent, multi-satellite systems. Collision avoidance and reconfiguration simulations were performed for a cluster of four satellites.

The ObjectAgent system is being developed to create an agent-based software architecture for autonomous distributed systems. Agents are used to implement all of the software functionality and communicate through simplified natural language messages. Decision-making and fault detection and recovery capabilities are built-in at all levels. During the first phase of development, ObjectAgent was prototyped in Matlab. A complete, GUI-based environment was developed for the creation, simulation, and analysis of multi-agent, multi-satellite systems. Collision avoidance and reconfiguration simulations were performed for a cluster of four satellites.

The ObjectAgent system is being developed to create an agent-based software architecture for autonomous distributed systems. Agents are used to implement all of the software functionality and communicate through simplified natural language messages. Decision-making and fault detection and recovery capabilities are built-in at all levels. During the first phase of development, ObjectAgent was prototyped in Matlab. A complete, GUI-based environment was developed for the creation, simulation, and analysis of multi-agent, multi-satellite systems. Collision avoidance and reconfiguration simulations were performed for a cluster of four satellites.

Monitoring is an essential process to observe and improve the reliability and the performance of large-scale distributed (LSD) systems. In an LSD environment, a large number of events is generated by the system components during its execution or interaction with external objects (e.g. users or processes). Monitoring such events is necessary for observing the run-time behavior of LSD systems and providing status information required for debugging, tuning and managing such applications. However, correlated events are generated concurrently and could be distributed in various locations in the applications environment which complicates the management decisions process and thereby makes monitoring LSD systems an intricate task. We propose a scalable high-performance monitoring architecture for LSD systems to detect and classify interesting local and global events and disseminate the monitoring information to the corresponding end- points management applications such as debugging and reactive control tools to improve the application performance and reliability. A large volume of events may be generated due to the extensive demands of the monitoring applications and the high interaction of LSD systems. The monitoring architecture employs a high-performance event filtering mechanism to efficiently process the large volume of event traffic generated by LSD systems and minimize the intrusiveness of the monitoring process by reducing the event traffic flow in the system and distributing the monitoring computation. Our architecture also supports dynamic and flexible reconfiguration of the monitoring mechanism via its Instrumentation and subscription components. As a case study, we show how our monitoring architecture can be utilized to improve the reliability and the performance of the Interactive Remote Instruction (IRI) system which is a large-scale distributed system for collaborative distance learning. The filtering mechanism represents an Intrinsic component integrated with the monitoring architecture to reduce the volume of event traffic flow in the system, and thereby reduce the intrusiveness of the monitoring process. We are developing an event filtering architecture to efficiently process the large volume of event traffic generated by LSD systems (such as distributed interactive applications). This filtering architecture is used to monitor collaborative distance learning application for obtaining debugging and feedback information. Our architecture supports the dynamic (re)configuration and optimization of event filters in large-scale distributed systems. Our work represents a major contribution by (1) survey and evaluating existing event filtering mechanisms In supporting monitoring LSD systems and (2) devising an integrated scalable high- performance architecture of event filtering that spans several kev application domains, presenting techniques to improve the functionality, performance and scalability. This paper describes the primary characteristics and challenges of developing high-performance event filtering for monitoring LSD systems. We survey existing event filtering mechanisms and explain key characteristics for each technique. In addition, we discuss limitations with existing event filtering mechanisms and outline how our architecture will improve key aspects of event filtering.

Monitoring is an essential process to observe and improve the reliability and the performance of large-scale distributed (LSD) systems. In an LSD environment, a large number of events is generated by the system components during its execution or interaction with external objects (e.g. users or processes). Monitoring such events is necessary for observing the run-time behavior of LSD systems and providing status information required for debugging, tuning and managing such applications. However, correlated events are generated concurrently and could be distributed in various locations in the applications environment which complicates the management decisions process and thereby makes monitoring LSD systems an intricate task. We propose a scalable high-performance monitoring architecture for LSD systems to detect and classify interesting local and global events and disseminate the monitoring information to the corresponding end- points management applications such as debugging and reactive control tools to improve the application performance and reliability. A large volume of events may be generated due to the extensive demands of the monitoring applications and the high interaction of LSD systems. The monitoring architecture employs a high-performance event filtering mechanism to efficiently process the large volume of event traffic generated by LSD systems and minimize the intrusiveness of the monitoring process by reducing the event traffic flow in the system and distributing the monitoring computation. Our architecture also supports dynamic and flexible reconfiguration of the monitoring mechanism via its Instrumentation and subscription components. As a case study, we show how our monitoring architecture can be utilized to improve the reliability and the performance of the Interactive Remote Instruction (IRI) system which is a large-scale distributed system for collaborative distance learning. The filtering mechanism represents an Intrinsic component integrated with the monitoring architecture to reduce the volume of event traffic flow in the system, and thereby reduce the intrusiveness of the monitoring process. We are developing an event filtering architecture to efficiently process the large volume of event traffic generated by LSD systems (such as distributed interactive applications). This filtering architecture is used to monitor collaborative distance learning application for obtaining debugging and feedback information. Our architecture supports the dynamic (re)configuration and optimization of event filters in large-scale distributed systems. Our work represents a major contribution by (1) survey and evaluating existing event filtering mechanisms In supporting monitoring LSD systems and (2) devising an integrated scalable high- performance architecture of event filtering that spans several kev application domains, presenting techniques to improve the functionality, performance and scalability. This paper describes the primary characteristics and challenges of developing high-performance event filtering for monitoring LSD systems. We survey existing event filtering mechanisms and explain key characteristics for each technique. In addition, we discuss limitations with existing event filtering mechanisms and outline how our architecture will improve key aspects of event filtering.

N-tier architecture has been more commonly used as a methodology for developing large database applications. This work evaluates the use of this architecture instead of the classical Client/Server architecture in developing corporate applications based on distributed databases. The comparison between architectures is performed using applications that execute transactions similar to those defined in the Transaction Process Council Type C benchmark (TPC-C). The environment used for development and testing was the AFIT Bimodal Cluster (ABC); a heterogeneous cluster of PCs, running Microsoft Windows NT 4.0 OS. The comparative experimental analysis demonstrated that the N-tier architecture allows more efficient bandwidth utilization between client and server machines, with similar performance. Results led to conclusion that the N-tier architecture is better suited than the Client/Server for use in corporate systems interconnected by low bandwidth Wide Area Networks (WANs), such as the Internet.

The paper presents a distributed component-oriented multi-tier architecture as applied to the multifunctional ECG software system development This approach makes it possible to design flexible and manageable ECG applications with the functionality that can be dynamically changed or extended. As a practical implementation of the elaborated architecture a realtime ECG system was developed and its performance parameters were investigated. A set of implemented components includes several realtime data acquisition modules, fast visualization and printing components as well as noise suppression and QRS detection and survey modules, The modular structure of the application with support of transparent integration of new components enabled us to develop additional add-on modules for carrying out specific experiments with ECG transmission methods,

We propose a distributed agent architecture (DAA) that can support a variety of paradigms based on both traditional real-time computing and artificial intelligence. DAA consists of distributed agents that are classified into two categories: reactive and cognitive. Reactive agents can be implemented directly in Ada to meet hard real-time requirements and be deployed on on-board embedded processors. A traditional real-time computing methodology under consideration is the rate monotonic theory that can guarantee schedulability based on analytical methods. AI techniques under consideration for reactive agents are approximate or anytime reasoning that can be implemented using Bayesian belief networks as in Guardian. Cognitive agents are traditional expert systems that can be implemented in ART-Ada to meet soft real-time requirements. During the initial design of cognitive agents, it is critical to consider the migration path that would allow initial deployment on ground-based workstations with eventual deployment on on-board processors. ART-Ada technology enables this migration while Lisp-based technologies make it difficult if not impossible. In addition to reactive and cognitive agents, a meta-level agent would be needed to coordinate multiple agents and to provide meta-level control.

No abstract available

In the article the methodology of construction of matrix models of motion of the architecture of computer systems is given. The offered principles of construction of computer networks with deep paralleling of information streams on the basis of two-dimensional and three-dimensional matrix models of data motion solve an actual scientific and technical problem of methodology of calculation of efficiency of data motion in such systems

We consider a low-complexity version of the Compute and Forward scheme that involves only scaling, offset (dithering removal) and scalar quantization at the relays. The proposed scheme is suited for the uplink of a distributed antenna system where the antenna elements must be very simple and are connected to a oint processor via orthogonal perfect links of given rate R0. We consider the design of non-binary LDPC codes naturally matched to the proposed scheme. Each antenna element performs individual (decentralized) Belief Propagation decoding of its own quantized signal, and sends a linear combination of the users' information messages via the noiseless link to the joint processor, which retrieves the users' messages by Gaussian elimination. The complexity of this scheme is linear in the coding block length and polynomial in the system size (number of relays).

Network programming language, dedicated for parallel programming in distributed systems based on ideology of multiprocessors with dynamic architecture (MDA) that provide automatic paralleling programs, high reliability of computations and unlimited scaling is considered. The language considered describes not the algorithm of the problem being solved but its initial structure that can be transformed during the process of solution. The language has two forms of program representation – graphic and text ones and completely releases the programmer from care of paralleling program and of computational resources used.

Ubiquitous sensing devices frequently disseminate their data between them. The use of a distributed event-based system that decouples publishers of subscribers arises as an ideal candidate to implement the dissemination process. In this paper, we present a network architecture which merges the network and overlay layers of typical structured event-based systems. Directional Random Walks (DRWs) are used for the construction of this merged layer. Our first results show that DRWs are suitable to balance the load using a few nodes in the network to construct the dissemination path. As future work, we propose to study the properties of this new layer and to work on the design of Bloom filters to manage broker nodes.

Ubiquitous sensing devices frequently disseminate their data between them. The use of a distributed event-based system that decouples publishers of subscribers arises as an ideal candidate to implement the dissemination process. In this paper, we present a network architecture which merges the network and overlay layers of typical structured event-based systems. Directional Random Walks (DRWs) are used for the construction of this merged layer. Our first results show that DRWs are suitable to balance the load using a few nodes in the network to construct the dissemination path. As future work, we propose to study the properties of this new layer and to work on the design of Bloom filters to manage broker nodes.