An extensible, ontology-based, distributed information system architecture

Distributed systems has been an area of intense activity over the past ten years. The subject is entering a stage of maturity with work now focusing on standards for open distributed processing (ODP). Recently, however, a number of new challenges have emerged for distributed systems. Among these challenges, distributed systems are increasingly having to support multimedia services, and this has raised a number of issues for distributed systems designers. One of the most important issues in this area is that of synchronization. Multimedia applications require sophisticated support for synchronization both to coordinate multimedia presentations and to maintain timing relationships between a number of real-time data transmissions. Current distributed system architectures do not support such services. The paper discusses the problem of incorporating support for synchronization in open distributed system architectures. It is argued that support must be provided for synchronization both in the invocation mechanism and in the form of new services called streams and synchronization managers. The proposals are compared to related work in the field.

Cronus [1-7] is an object oriented distributed system which operates in a heterogeneous computer environment of interconnected local area networks. As a distributed system architecture. Cronus faces a number of resource management issues not present in non-distributed architectures. Strategies for effectively controlling the redundancy and reconfigurability inherent in Cronus are needed to take advantage of the distributed system environment. These strategies for resource management are often conveniently separated into policies and mechanisms. A policy is a goal or guideline set by a system administrator or component designer constraining the decisions made by a resource allocator. A mechanism is an internal system structure designed to implement a class of policies.In the Cronus distributed system model, there are currently two general aspects of resource allocation mechanisms which are particular to the network environment and must be effectively managed. One of these is the binding of a client request to a particular resource manager for those resources which are available redundantly. Redundancy comes in two forms: replicated objects, (e.g., a multi-copy file) and replicated managers (any manager for a type can create a new instance of that object type). For both forms the selection of an object manager to provide the given service is an important resource management policy decision. The other important aspect of resource management mechanism is the ability to reconfigure parts of the system by dynamically migrating objects. Object migration is a powerful tool for matching system resources to tasks in a manner that attempts to maximize some measure of system performance, reliability, or survivability. Both static reconfiguration (e.g., choosing or amending the placement of object managers and their associated objects), and dynamic reconfiguration (e.g., moving an individual object in direct response to demand for its use possible in the Cronus architecture and design.The general approach to resource management in Cronus is to individually control the management of the classes of objects which make up the system. This approach extends Cronus resource management concepts beyond system resources to the abstract resources developed by applications. Resource management for an individual abstract resource (type) and for groups of related resource types (services) in Cronus is based on combining a number of carefully planned mechanisms which are part of the system architecture. In addition to resource management by resource type, a client specific policy which considers collections of object types used in a specific context can be constructed.In Cronus we achieve system wide and easily controllable resource management by requiring the object managers to cooperate in enforcing a resource management policy for their resource type. An object manager can redirect operations to a peer manager on another processor on the basis of current resource status. In the case for creation of a file to an alternate file manager which may have more storage available. Part of the basis for decisions to redirect requests are parameters, settable dynamically by system administrators through monitoring and control functions, which control the resource management strategy. The creation of objects and resource management in general thus becomes a responsibility that is decentralized among object managers on each processor based on a global allocation policy, both in terms of sharing current status and possible redirection of operations between managers.The Cronus resource management model is based on the integration of the following set of primitive mechanisms: the kernel routes requests for a given type to any available manager of that type, using the Locate mechanismCronus managers redirect requests to a more appropriate peer to accomplish resource management objectivesmanagers periodically collect current status of their peers, via a standard mechanism (ReportStatus), to be used as a basis for selecting a site for redirecting an operationusers and applications optionally indicate specific location preferences with requestsan operator can monitor and regulate the functioning of the resource management policyapplications can use the basic system mechanisms (e.g. broadcast or multicast, ReportStatus operations) to build special-purpose resource management strategies tailored to their needThere is a hierarchy of desirable locations for implementing resource management policies: object managers, shared libraries, and finally client programs or users themselves. Managers are the most desirable because they are readily identifiable with a limited set of object types which are likely to have similar policy goals. Also, managers are addressable as a group for administrative control to regulate the policy parameters, and for peer manager cooperation to implement the policy. Many decisions are negotiated between managers based upon information periodically obtained via the ReportStatus operation. The Cronus Monitoring and Control System uses the same ReportStatus operation to present the operator with a global view of how well the resource management policy is proceeding.In this paper we elaborate on these approaches to distributed resource management in Cronus, including appropriate background, detailed system design, and experiences with incorporating these ideas into three different resource managers.

The Aerospace Corporation has independently developed a distributed electric power system for picosatellites. This distributed power system architecture is being implemented on a number of upcoming picosatellite missions. The first implementation of this architecture will be flown on the PowerSphere Flight Experiment and the Pico Satellite Inflatable Reflector Experiment (PSIREX). To date all of the picosatellite missions do not have attitude control or deployable solar array structures. Solar cells are body mounted on the various sides of the picosatellite. The architecture was conceived to solve the problem of obtaining the maximum amount of electric power from a solar array, that has multiple panels, that are not arranged on a single planar surface. Aerospace Corporation researchers working on developing viable power systems for picosatellites were awarded patents 6,127,621 October 2, 2000 Power Sphere and 6396167 B1 May 28, 2002 Power Distribution System for this unique solution for distributed power system architecture for a multifaceted solar array. The authors have developed a prototype of the ring bus and have completed initial testing of its performance.

In this paper, the distributed fault-tolerant computer middleware of deterministic communication is designed, under the distributed system architecture; key technologies such as distributed node synchronization/communication technology, distributed system membership management, and membership consistency guarantee are mainly discussed. First, the distributed fault-tolerant computer architecture and related technologies of deterministic communication are introduced, then the software design is explained, and the design and implementation of middleware software are mainly discussed.

This article explores the world of dependable systems, specifically focusing on system design, software solutions, and architectural decisions that facilitate collaborative work on shared text documents across multiple users in near real time. It aims to dive into the intricacies of designing robust and effective document collaboration software focusing on understanding the requirements of such a system, the working principle of collaborative text editing, software architecture, technology stack selection, and tooling that can sustain such a system. To examine the pros and cons of the proposed system, the paper will detail how collaborative text editing software can benefit from such an architecture regarding availability, elasticity, and scaling. The intricate nature of this system renders this paper a valuable resource for prospective investigations within the domain of dependable systems and distributed systems. This research first examines the requirements of a real-time collaboration system and the necessary core features. Then, it analyzes the design, the application structure, and the system organization while also considering key architectural requirements as the necessity of scaling, the usage of microservices, cross-service communications, and client–server communication. For the technology stack of the implementation, this research considers the alternatives at each layer, from client to server. Once these decisions are made, it follows system development while examining possible improvements for the issues previously encountered. To validate the architecture, a testing strategy is developed, to examine the key capabilities of the system, such as resource consumption and throughput. The conclusions review the combination of modern and conventional application development principles needed to address the challenges of conflict-free document replication, decoupled and stateless event-driven architecture, idempotency, and data consistency. This paper not only showcases the design and implementation process but also sets a foundation for future research and innovation in dependable systems, collaborative technologies, sustainable solutions, and distributed system architecture.

The separation of architecture definition language (ADL) and interface definition language (IDL) is widely accepted in the distributed system community. It separates issues of hierarchical composition and configuration from those of services, communication and synchronisation and thus eases reconfiguration without changing the interfaces and implementation and allows the change of services within well-defined configuration constraints. Our approach towards distributed system definition draws on the Darwin project's notion of distributed system architecture definition and on Eiffel's notion of design-by-contract. We extend contracts to deal with synchronisation and coordination at a higher level, explicitly targeting both large-scale loosely-coupled distributed components and tightly coupled parallel or multithreaded objects. In this paper we present a Java binding of the resulting contract extensions. We incorporate annotations into Java programs adding Eiffel-style assertions and other contractual constraints. Java component code and constraints are then associated to architectural diagrams in a visual programming environment. The paper illustrates the language features in a case study of a lift control system. Based on the case study, the component-based design approach is illustrated and the internal synchronisation of method execution is explained.

The Direct Access File System (DAFS) is a distributed file system built on top of direct-access transports (DAT). Direct-access transports are characterized by using remote direct memory access (RDMA) for data transfer and user-level networking. The motivation behind the DAT-enabled distributed file system architecture is the reduction of the CPU overhead on the I/O data path.We have created an implementation of DAFS for the FreeBSD platform. In this paper we describe the performance evaluation study of DAFS that we have performed using this software. The goal of this study is to determine whether the architecture of DAFS brings any fundamental performance benefits to applications compared to traditional distributed file systems, such as NFS. We perform comparison of DAFS to a version of NFS optimized to reduce the I/O overhead. In order to thoroughly understand the impact of DAFS on application performance, we consider a diverse range of applications workloads.We conclude that DAFS can accomplish superior performance for latency-sensitive applications, outperforming NFS by up to a factor of 2. Bandwidth-sensitive applications do equally well on both systems, unless they are CPU-intensive, in which case they perform better on DAFS. We also found that RDMA is a less restrictive mechanism to achieve copy avoidance than that used by the optimized NFS.

In distributed power system architectures, the DC/DC conversion stage turns out to be an onboard converter with very stringent specifications, particularly in terms of efficiency and size. Practical implementations of four DC/DC converters based on PWM, quasi-resonant, and multiresonant topologies are compared for a telecommunications onboard application. Experimental results concerning efficiency, component stresses, EMC behavior and size are provided, and a comparative analysis based on these data is performed. >

This chapter discusses architectural aspects of Distributed Knowledge Base Management Systems. We investigate how research results on knowledge representation from the artificial intelligence side and on massive data management from the database side may be effectively combined in the design and development of a future distributed knowledge base management system architecture. In particular we address the incorporation of preexisting, autonomously created and administered, heterogeneous database systems as components in a Distributed Knowledge Base Management System and we illustrate how a relational data base schema may be translated into a semantic data model using the Temporal Hierarchic Model [FN85, SCHI83b] as the representation tool.KeywordsKnowledge RepresentationDatabase AdministratorDatabase SchemaLocal DatabaseData DictionaryThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

The process of developing policies and laws that apply to energy the manufacturing, distribution, and consumption phases systems is known as energy system policy-making. Energy policies are important in directing the growth and evolution of energy systems, providing security of supply, promoting sustainability, and helping to mitigate climate change. Energy sector development is critical for societal advancement, economic prosperity, and environmental sustainability. It incorporates a wide range of potential energy sources such as nuclear power, energy from renewable sources, along with fossil fuels (including sunlight, breeze, water, as well as natural gas). To cut greenhouse gas emissions, battle climate change, and achieve an environmentally friendly and less costly energy future, the world must prioritize the transition to a more resilient and sustainable energy system. The formulation of energy system policy involves a variety of stakeholders, including governments, regulatory bodies, energy companies, industry groups, environmental protection organizations, and the general public. These stakeholders collaborate to establish the objectives of energy policy, develop strategies, and implement the plans. energy system policy is critical in combating climate change due to how it encourages the use all energy produced from renewable sources, efforts to improve energy efficiency, and low-carbon technology. in order to attain aggressive emission reduction targets, research in this sector can give knowledge on effective policy formulation, implementation tactics, and evaluation frameworks. as the world progresses approaching an economy with fewer greenhouse gases, it is critical to understand the causes, impediments, and consequences of the shift to cleaner energy. research can assist identify the optimum governance structures, market mechanisms, and regulatory frameworks for facilitating the changeover to renewable energy sources while achieving carbon reduction goals. access to affordable, dependable energy services is essential for socioeconomic development and the eradication of poverty. research has the potential to shed light on the financial plans and legislative frameworks that might increase access to energy, especially in neglected areas, while addressing concerns of poverty and inequality. In order for the energy system to keep up with technological advancement, policy makers must encourage the use of cutting-edge energy technology. research may give decision-makers knowledge about emerging technologies, prospective implications, and the regulatory frameworks necessary to promote their acceptance and integration into the energy system. In this research we will be using weighted sum method. Clean fossil fuel power generation, natural gas combined cycles (ngcc), integrated gasifier combined cycles (igcc), improved transmission and distribution systems, decentralized power-fuel cells, decentralized power-micro-turbines. Evaluation parameters: impact on energy and carbon intensity, impact on security, impact on energy security, status and technological potential, barriers to commercial use. Result: the WSM method of Ranking Energy System Policy Making in Natural Gas Combined Cycles (NGCC) is got the first rank whereas is the Decentralised Power-fuel Cells is having the Lowest rank. The WSM method of Ranking Energy System Policy Making in Natural Gas Combined Cycles (NGCC) is got the first rank whereas is the Decentralised Power-fuel Cells is having the Lowest rank.

Recent years have seen increased interest in green technologies such as photovoltaic (PV) electricity and plug-in hybrid electric vehicles (PHEVs). Such technologies, however, have been found to be detrimental to distribution networks. This paper introduces a novel distribution system architecture that can better accommodate the expected growth in PV electricity and PHEVs. In the proposed architecture, the distribution system becomes a bilayer system composed of the traditional ac layer that serves existing system loads, plus an embedded dc layer that interfaces with PV arrays and PHEVs. A bidirectional converter interconnects the two layers and controls the power flows between them. This paper presents the key design and operational aspects of the proposed architecture, with consideration of different uncertainties inherent in the system. To this end, a probabilistic benchmark has been developed for modeling these uncertainties and for use with the sizing and scheduling of different system components. Monte Carlo (MC) simulations confirmed the technical and economic merit of the proposed design methodology.

Historically, electric power distribution systems were considered passive subsystems served by the larger transmission grid. Recently, smart grid initiatives have driven the evolution of distribution systems into active systems with market-aware customers and distributed power generation. Along with more diverse and complex injections, contemporary distribution systems are equipped with additional sensing equipment, two-way communications networks, and advanced metering infrastructure (AMI). These are essential technologies that enable several core functions of a smart grid, including real-time monitoring and online control. This thesis presents several tools for the online analysis and control of modern electric power distribution systems. "Online" refers to a control framework that can react to changing system conditions in order to maintain static security and meet different operating objectives. Specifically, the objective of this research is to integrate temporal information (i.e., forecasts) into distribution system analysis tools while maintaining fundamental engineering requirements by re-examining classical problems through a contemporary lens. Connected by an underlying injection forecast model, three research topics are explored: 1) distribution load capability, 2) analytical time window selection for quasi-static time series (QSTS) analysis, and 3) distribution state estimation with explicit consideration of non-synchronized measurements. The work proposed here is a necessary step towards distribution system optimization in an online setting with uncertain and/or bidirectional power flows.

There are goals within military signal processing systems which can best be met by the use of distributed processing techniques. For example, the goal of application flexibility is met by using several interconnected general purpose processing elements and/or signal conditioning elements that can be changed by software or microcode to perform a suitable range of tasks. This paper presents an application of fiber optic technology in the communication path of a distributed system architecture for military systems. The following paragraphs provide a description of the application architecture followed by a description of the fiber optic role in the system.There are goals within military signal processing systems which can best be met by the use of distributed processing techniques. For example, the goal of application flexibility is met by using several interconnected general purpose processing elements and/or signal conditioning elements that can be changed by software or microcode to perform a suitable range of tasks. This paper presents an application of fiber optic technology in the communication path of a distributed system architecture for military systems. The following paragraphs provide a description of the application architecture followed by a description of the fiber optic role in the system.

As computers continually improve in performance and decrease in manufacturing cost, distributed systems consisting of multiple computers implemented as parallel computation platforms have become viable for engineering applications which demand intensive computation power. This paper proposes an extended version of a previously developed low cost parallel computation platform called para worker. The system is based on a cluster structure which is a form of a distributed system. The new system is termed para worker 2 which differentiates it from the earlier system. The new proposed system adds enhanced features of improved dynamic object reallocation, adaptive consistency protocols, and location transparency. Performance of the para worker 2 has proven to be superior to the para worker. Testing was based on an execution of Genetic Algorithm to solve the Economic Dispatch problem in Power Engineering. The proposal is particularly useful for the implementation and execution of computational intelligence techniques such as evolutionary computing for engineering applications.

Effective interaction with distributed databases means providing the user with location transparency, i.e. it should appear as if the data is located at a single site. One major challenge in obtaining location transparency is the integration and presentation of heterogeneous, distributed data in near-real time with a user-friendly Web-based interface. This paper describes two projects that apply intelligent agents to the problem of integrating and presenting heterogeneous distributed data. The first project is a Web-based, simulation scenario-generating application that integrates data from distributed sources to build a simulation scenario for an interactive wargaming simulation called Janus. This scenario-generating application is called the Dynamic Scenario Builder (DSB) and will ultimately integrate data from the US Army's Functional Description of the Battlespace (FDB) with Janus or other simulation databases to generate simulation scenarios. The second project involves the development of a system to enable logistics planners to access distributed databases from remote locations and autonomously update data sources such that modifications are dynamically mirrored and displayed to all users of the distributed system. A key feature of this research is the visual presentation of the summarized information in a meaningful manner such that drilling down to more detailed information is evident. This project applies a platform for mediators called HERMES (Heterogeneous Reasoning and Mediator System) as a means of data integration from several heterogeneous distributed databases.