Distributed Object Model Research Articles

AdoB: Bridging Benign and Byzantine Consensus with Atomic Distributed Objects

Achieving consensus is a challenging and ubiquitous problem in distributed systems that is only made harder by the introduction of malicious byzantine servers. While significant effort has been devoted to the benign and byzantine failure models individually, no prior work has considered the mechanized verification of both in a generic way. We claim this is due to the lack of an appropriate abstraction that is capable of representing both benign and byzantine consensus without either losing too much detail or becoming impractically complex. We build on recent work on the atomic distributed object model to fill this void with a novel abstraction called AdoB. In addition to revealing important insights into the essence of consensus, this abstraction has practical benefits for easing distributed system verification. As a case study, we proved safety and liveness properties for AdoB in Coq, which are the first such mechanized proofs to handle benign and byzantine consensus in a unified manner. We also demonstrate that AdoB faithfully models real consensus protocols by proving it is refined by standard network-level specifications of Fast Paxos and a variant of Jolteon.

Masquerading a Networked Embedded Computer as a Remote Object Using an Asynchronous Remote Object Protocol for a System With Small Servers

There are increasing demands for making multiple sensors/devices accessible over a wireless local area network (WLAN) for measurement, control, and monitoring purposes. Such a system comprises a client, and multiple small embedded computer-based servers deployed in remote places. To apply the advantage of distributed object models, such as Java Remote Method Invocation (RMI), the model cannot work on an embedded computer because it demands sufficient resources, including the processing power of the central processing unit, memory, and an operating system. The model provides synchronous operations using the Transmission Control Protocol/Internet Protocol with heavy overheads, which results in low throughput compared with the lightweight User Datagram Protocol. A simple asynchronous remote object protocol for embedded computers (eASROP) is designed and implemented to enable an embedded computer and its acquired data to masquerade as an RMI-compatible remote object on a server. The client is not blocked after it makes a remote method call to a server, and can continue its job. The client can asynchronously receive a return object that contains status data and control data. The results of performance measurements obtained in experiments demonstrated that for the eASROP on an embedded computer-based server (48 MHz), the extra execution time that the client experienced was 1.67–15.4% of that for the RMI on a personal-computer-based server (3.1 GHz, 4 cores) on a WLAN.

Asynchronous Distributed Object Model Using Java for the Control System of a Synchrotron Radiation Source

A simple distributed object model, called an asynchronous distributed object protocol (ADOP), was designed and implemented as middleware for a control system of a synchrotron radiation source. The ADOP replaces time-constrained parts of the control system that were previously based on the Java Remote Method Invocation (RMI) model. Under RMI’s synchronous communication, when a client executes a remote-method invocation for a device/component to be controlled on a remote server, the client is suspended until the server sends a result back to the client after completing the control sequence. Using the ADOP, even in a multi-client environment, clients are not blocked when they make remote-method invocations with an object parameter/return object that includes short control data associated with the event data, status data, and setting data for the devices/components. The clients can asynchronously receive resultant control data from the remote servers. Performance measurements obtained in experiments demonstrate that the ADOP had an execution time that was 1.4–13.1% of the RMI’s execution time.

Developing JAVA Card Application with RMI API

Abstract This paper describes research in the use of the RMI to develop Java Card applications. the Java Card RMI (JCRMI), which is based on the J2SE RMI distributed-object model. In the RMI model a server application creates and makes accessible remote objects, and a client application obtains remote references to the server's remote objects, and then invokes remote methods on them. In JCRMI, the Java Card applet is the server, and the host application is the client.

Gird manufacturing: a new solution for cross-enterprise collaboration

Industry has put forward demands on cross enterprises collaboration including various resources sharing. In order to meet these demands, much has been done to realize cross-border collaboration. However, after analyzing the unique features of manufacturing resources and the limits of existing technologies like Internet, EC, ASP and Web-based design/manufacturing, which adopt many new Web technologies like Web mark-up languages, Web-based client–server programming tools and distributed object modeling methods, it is concluded that all these technologies could not meet industrial demands on dynamic sharing of various resources. Therefore grid manufacturing is put forward to meet these demands. According to the features of resources to be shared and the technologies to be used, grid manufacturing distinguishes itself from Web-based manufacturing by providing the transient services and by achieving the interoperability. The differences and relationship between grid manufacturing and grid computing are yielded. At last, a Web service-based architecture of grid manufacturing is proposed and the related technologies are summarized.

Collaborative object-oriented visualization environment

In this paper, we present a Collaborative Object-oriented Visualization Environment (COVE) which provides a flexible and extensible framework for collaborative visualization. COVE integrates collaborative and parallel computing environments based on a distributed object model. It is built as a collection of concurrent objects: collaborative and application objects which interact with one another to construct collaborative parallel computing environments. The former enables COVE to execute various collaborative functions, while the latter allows it to execute fast parallel visualization in various modes. Also, flexibility and extensibility are provided by plugging the proper application objects into COVE at run-time, and making them interact with one another through collaboration objects. For our experiment, three visualization modes for volume rendering are designed and implemented to support the fast and flexible analysis of volume data in a collaborative environment.

Asynchronous Remote Event Notification Using a Distributed Object Model for Heterogeneous Remote Monitoring Systems and Control Systems at the 1.8-GeV Tohoku Synchrotron Radiation Source

An asynchronous remote event notification (AREN) for heterogeneous remote monitoring systems and distributed control systems has been developed using a distributed object model, Java remote method invocation (RMI), for the 1.8-GeV synchrotron radiation source at the Tohoku Synchrotron Radiation Facility (TSRF), which will have fifty beamlines for soft X-ray researches. The beamlines are controlled by distributed control systems composed of fifty outlying node computers and eleven remote monitoring systems connected to a network. There are more than three thousand event status signal data available from the beamlines. The event status signal data are transition status signals generated at any instance by valves/shutters, driving units, and safety interlocks when closing/opening. To acquire such event signal data, the monitoring system had to make continuous synchronous inquiries (CSI) or performed polling for an outlying node over the network. However, the monitoring system must synchronously wait each time until the outlying node transmits event status data back to the monitoring system, causing an unacceptable low event rate of approximately 40 events/second and heavy CPU load. On detecting a transitional change in an event status signal of a component, AREN automatically sends event status signal data to the monitoring systems over the network. Performance measurements proved that AREN increased the maximum event rate by one order of magnitude compared with that of CSI. By using AREN, the monitoring systems are capable of predicting signs that suggest malfunctioning of a beamline component at TSRF. The design and performance of AREN for monitoring systems and control systems for the synchrotron radiation source are described in this paper

DCOM and MMS–based control software architecture for automated manufacturing system

In this paper, we introduce the manufacturing message specification (MMS) and compare two distributed object approaches–distributed component object model (DCOM) and common object request broker architecture (CORBA), suggest characteristics that DCOM is more suitable for automated manufacturing system (AMS) control software integration. In order to make a control system provided with interoperability and reconfigurability etc., a hybrid control system is built for AMS, then a control software architecture is presented for AMS based on distributed object DCOM middleware and MMS standard. The object-oriented DCOM communication protocol is used to implement the MMS in a distributed object mode. DCOM and MMS combination brings the operating system independent communication capabilities to manufacturing devices such as CNC machine tools and industrial robots in AMS. Control software implementation of MMS concepts in the DCOM environment is particularly discussed. Finally, to verify the control software architecture for AMS, prototype development has been implemented in VC++ 6.0 developer environments.

Performance Modeling and Analysis of Distributed Object-Oriented Software

Information systems are basically distributed while object oriented brings new issues in software engineering. Pairing distributed systems with object paradigms results in a distributed object model. Choosing the appropriate distributed object model is a multi-criteria decision problem. Performance is a key criterion that makes software developers be able to select the object-oriented system that best fit their requirements. The accuracy of the performance evaluation depends strongly on the ability to model and analyze the features of the target software. Classical techniques and methodologies of performance analysis are either unsuitable or unnatural to capture performance behavior of Object-Oriented (OO) systems. In this paper, we present Performance-Based Model for Distributed Object-Oriented Software (DOOS) and a methodology to analyze and evaluate its performance. The new model evaluates the overall time cost of DOOS system considering the communication overheads while preserving the OO features such as encapsulations, information hiding, inheritance, ...etc.

Distributed control system using a remote distributed object model for 1.8-GeV synchrotron radiation beamlines at TSRF

A distributed control system has been developed to control synchrotron radiation beamlines for the 1.8-GeV storage ring at Tohoku Synchrotron Radiation Facility (TSRF), Tohoku University, which has 50 beamlines for soft X-ray optics/microscopy, lithography, and biomaterial research. The system is composed of outlying nodes and remote operator consoles connected to a network. Each beamline is controlled by its own outlying node independently of adjacent beamlines in accordance with physics experimental requirements. The control system protects ultra-high vacuum components of the beamline and the storage ring by closing valves/shutters upon detecting a vacuum failure. The system was implemented using a distributed object model, Java remote method invocation (RMI). The control system provides information on the operation of the beamlines to remote clients such as operator consoles over the network in order to operate the TSRF. The design and implementation of the distributed control system as well as the control scheme for the synchrotron radiation beamlines at TSRF are described in this paper.

Distributed object models for collaboration in the construction industry

Information about products for the construction industry is increasingly often provided to designers in digital ways that enable them to apply the information directly in the design process. Digital product catalogues are provided using various media and formats and several initiatives are taken by the industry and by CAD developers to integrate this kind of information into CAD systems. Generally, current practice is to distribute the information to designers, for example, by using CD-ROMs or a website where the information can be downloaded. In our research, we recognise that distributing information in this manner detaches it from the business processes in the construction supply chain, which is a major disadvantage. The project presented in this paper concerns the implementation in the Dutch construction industry of a methodology for sharing product information through a distributed object model. The methodology, which is called Concept Modelling, forms a generic basis for the support of collaborative design, but is applied in this project to the integration of information from the supply chain in the design process. Through the distributed object model, design information and product information can be integrated while the actual data objects remain at their source. This enables the supply chain to provide information of a high semantic level to designers while keeping the control over the information and maintaining the relationship of the information with their business processes. The advantages of this approach in which information is shared, rather than exchanged, are numerous. Redundancy of information is minimised, consistency is improved, and updated information is available immediately. Moreover, design and construction processes can benefit significantly from the dynamic aspects of accessing information that is tied to business processes in the supply chain. For example, product selection during design can be based on latest information on product details, prices, production methods, and variants of products. This information can be provided to designers automatically and on demand.

Performance Analysis of Distributed Object Middleware

Java and distributed object models are important for building modern, scalable and interoperable applications. This paper is focused on the comparison and performance analysis of four important distributed object models for Java: RMI (Remote Method Invocation) and RMI-IIOP (Remote Method Invocation over Internet Inter-ORB Protocol), CORBA and DCOM. The paper presents a detailed performance analysis of the models and an overhead analysis to identify the bottlenecks in the models.

Design And Implementation Of A Static Bridge Between Com And Corba Distributed Objects

The distributed object standards Component Object Model (COM) and Common Object Request Broker Architecture (CORBA) apply object technology to design and use software components. While COM forms a good front end for the Microsoft Systems, CORBA is well suited for middle tier and back end Unix servers. By integrating them, the user can get a combination of the best attributes of both the systems. Bridging software is needed to transparently couple components from both the systems. This paper discusses a static method of achieving COM/CORBA interworking using a generic IDL compiler. It maps the COM and CORBA IDLs onto an intermediate representation from which stubs and skeletons are generated. Further, threading is used to allow multiple COM clients to contact a single CORBA server using Internet Interoperable Protocol / Transmission Control Protocol (IIOP/TCP) as a communication medium. To improve the networking speed and to bring about multicasting, IIOP/UDP has also been tried as a communication medium. The Object Reference (OR) from the implementation repository (IMR) and the Object Identifier (OID) from the registry have also been cached to improve the speed of the name lookup mechanism.

Solving irregularly structured problems based on distributed object model

This paper presents a distributed object model called MOIDE (multi-threading object-oriented infrastructure on distributed environment) for solving irregularly structured problems. The model creates an adaptive computing infrastructure for developing and executing irregular applications on distributed systems. The infrastructure allows dynamic reconfiguration to match the evolution of irregular computation and available system resources. A unified communication mechanism is built to integrate different communication paths on heterogeneous systems to support efficient communication. Autonomous load scheduling approach is proposed for dynamic load balancing. A runtime system is developed to implement MOIDE-based computing. Applications including N-body problem, ray tracing, and conjugate gradient are developed to demonstrate the advantages of the model.

Distributed object model for collaborative CAD environments based on design history

This paper presents new concepts for distributed dynamic design environments that deal with three aspects not effectively considered by the design literature in an integrated way: design history, CAD data model, and virtual prototyping. The present work details a design history model that gives support to views of higher levels than those usually found in design journals of CAD systems. The dynamic nature of the distributed environment is provided by an innovative mechanism that is not dependent on CORBA's DII or any other specialized middleware structure. Moreover, this paper presents an effective integration of a geometry bus on the top of a communication layer with strong support to mutant distributed objects at run time.

分散オブジェクト技術を用いた機能分散型外科手術支援ディスプレイシステムの開発

分散オブジェクト技術を用いた機能分散型外科手術支援ディスプレイシステムの開発

Web-based knowledge-intensive support framework for collaborative design of MEMS

Microelectromechanical systems (MEMS) design and manufacturing are inherently multi-physical and multi-disciplinary; no single person is able to perform a full development process for a MEM device or system. In this paper we develop a WWW-based design platform for collaborative design of MEMS. The proposed web-based distributed object modeling and evaluation framework with client-knowledge server architecture, KS-WebDOME, allows multi-users/designers in different locations to participate in the same design process. Under this framework, concurrent integrated MEMS design and simulation models can be built using both local and distributed resources, and the design collaboration can be realized by exchanging services between modules based upon CORBA standard communication protocol. To facilitate the rapid construction of the concurrent integrated design models for MEMS, a prototype design system, Web-MEMS Designer, is implemented through concurrent integration of multiple distributed and cooperative knowledge sources and software. By use of the developed prototype system, MEMS design and simulation can be carried out simultaneously and intelligently in an integrated but open design environment on the web. The case of a microgripper design for micro-robotic assembly systems is provided to illustrate how designers in different teams and organizations may participate and collaborate in MEMS design.

A Framework for Evaluating Distributed Object Models and its Application to Web Engineering

The success of building distributed object systems depends on important factors such as architecture, the distributed object model (DOM) selected, and the process adapted in the selection of the DO...

Scalable architecture for parallel distributed implementation of genetic programming on network of workstations

Abstract We present an approach for developing a scalable architecture for parallel distributed implementation of genetic programming (PDIGP). The approach is based on exploitation of the inherent parallelism among semi-isolated subpopulations in genetic programming (GP). Proposed implementation runs on cost-efficient configurations of networks on workstations in LAN and Internet environment. Developed architecture features single global migration broker and centralized manager of the semi-isolated subpopulations, which contribute to achieving quick propagation of the globally fittest individuals among the subpopulations, reducing the performance demands to the communication network, and achieving flexibility in system configurations by introducing dynamically scaling up opportunities. PDIGP exploits distributed component object model (DCOM) as a communication paradigm, which as a true system model offers generic support for the issues of naming, locating and protecting the distributed entities in proposed architecture of PDIGP. Experimentally obtained results of computational effort of proposed PDIGP are discussed. The results show that computational effort of PDIGP marginally differs from the computational effort in canonical panmictic GP evolving single large population. For PDIGP running on systems configurations with 16 workstations the computational effort is less than panmictic GP, while for smaller configurations it is insignificantly more. Analytically obtained and empirically proved results of the speedup of computational performance indicate that PDIGP features linear, close to ideal characteristics. Experimentally obtained results of PDIGP running on configurations with eight workstations show close to 8-fold overall speedup. These results are consistent with the anticipated cumulative effect of the insignificant increase of computational effort for the considered configuration and the close to linear speedup of computational performance.

Object Clustering for High Performance Parallel Computing

In this article we present a new parallel programming environment, called distributed object-oriented virtual computing environment (DOVE), for clustered computers based on distributed object model. In DOVE, a parallel program is built as a collection of concurrent objects each of which has its own computing power and which interacts with one another by remote method invocation. The parallelism is encapsulated within distributed objects, which can be handled the same way as local objects. The main goal of DOVE is to provide users with an easy-to-use transparent parallel programming environment while supporting efficient parallelism encapsulated and distributed among objects. For the experiment and evaluation of DOVE, two parallel application programs have been developed both on DOVE and PVM.