Distributed Component Object Model Research Articles

Standalone OPC UA Wrapper for Industrial Monitoring and Control Systems

OPC unified architecture (UA), a communication standard for the manufacturing industry, enables exchanging control and management data among distributed entities in industrial automation systems. OPC UA wrapper is a migration strategy that provides UA clients with seamless access to legacy servers having OPC classic interfaces. This paper presents the design of a standalone OPC UA wrapper and discusses its performance through extensive experiments using a prototype implementation. The wrapper consists of two main components, i.e., UA server and classic client, which communicate with each other via shared memory and semaphore. One important feature of the design is that it employs a distributed component object model runtime library implemented in Java for platform independence. This makes it possible to build a cost-competitive wrapper system by using commercial off-the-shelf non-Windows solutions with low-cost microprocessors. Another key feature is the event-driven update interface between the UA and classic components, which we propose as an alternative to the sampling-based mechanism for the reduced delay. Through experiments using workloads from an industrial monitoring system, we present a systematic approach of identifying the system parameters having a direct impact on the wrapper performance and eventually tuning them such that the read and subscription services of OPC UA exhibit the best performance.

Research for Distributed Automatic Test System

Along with the development of computer and network technology, a distributed automatic test system works in a local area network is on the date. There are very great significance to investigate the follow topics, how to manage the resource in the ATS, how to find and drive the instrument in the ATS. This article combines the technology of distributed component object model and active directory Service, realized an open test system architecture.

Positioning Control of the Large Electric Flatcar via a Web Browser in Combination with Another System

Target strength (TS) of fish is an important parameter when we convert acoustic integration values obtained during acoustic surveys into estimates of fish abundance. The target strength pattern is measured by combining the rotation system for tilting the aspect of the sample with the echo data acquisition system using underwater ultrasonic waves. A user interface of network architecture was designed for collaborative use with researchers working in other organizations. The flexible network architecture is based on a web direct-access model for the rotation system. The user interface can monitor and control the rotation system via a web browser that is installed in any PC (personal computer) as a terminal. However, previously the combination of those two systems was performed not by using a web browser but by an exclusive interface program. Here we propose a connection model which provides indirect communication via DCOM (Distributed Component Object Model) server between these two systems. The connection model is added in the web direct-access model. This connection model can perform automatic measurements and allow combined manipulation between the rotation system and the echo measurement per degree via a web browser. In this paper, this connection model is detailed and was successfully implemented to the measurement system of an electric flatcar in a large tank.

An agent-based intelligent control platform for industrial holonic manufacturing systems

New revolutionary manufacturing paradigms, which take advantage of the newest emerging mechatronics, information, and communication technologies, and integrate them in a highly dynamic and agile economic, technical, and organizational manufacturing environment, are being researched and developed since the last decade of the 20th century. This new generation of manufacturing systems is referenced as intelligent manufacturing systems (IMS), and both the "holonic manufacturing system" (HMS) and the "agent-oriented manufacturing system" paradigms have been presented in recent years as the basis for making such systems a reality. This paper reports on the design and realization of an agent-based intelligent control system for industrial manufacturing systems, which covers both conventional mechatronics equipment and embedded control agents. The agent-based control software components are implemented as Windows NT services and logic control programs and interfaced via distributed component object model (DCOM) and Ethernet. Results of the application in an industrial manufacturing environment are used to show the effectiveness of the proposed "Holonic" approach.

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.

Component Object Based Single System Image for Dependable Implementation of Genetic Programming on Clusters

We present a distributed component-object model (DCOM) based single system image (SSI) for dependable parallel implementation of genetic programming (DPIGP). DPIGP is aimed to significantly and reliably improve the computational performance of genetic programming (GP) exploiting the inherent parallelism in GP among the evaluation of individuals. It runs on cost-effective clusters of commodity, non-dedicated, heterogeneous workstations or PCs. Developed SSI represents the pool of heterogeneous workstations as a single, unified virtual resource – a metacomputer, and addresses the issues of locating and allocating the physical resources, communicating between the entities of DPIGP, scheduling and load balancing. In addition, addressing the issue of fault tolerance, SSI allows for building a highly available metacomputer in which the cases of workstation failure result only in a corresponding partial degradation of the overall performance characteristics of DPIGP. Adopting DCOM as a communicating paradigm offers the benefits of software platform- and network protocol neutrality of proposed approach; and the generic support for the issues of locating, allocating and security of the distributed entities of DPIGP.

A comparative study of SOAP and DCOM

Simple Object Access Protocol (SOAP) is a recent technology, which aims at replacing traditional methods of remote communications, such as RPC-based Distributed Component Object Model (DCOM). Being designed with a goal of increasing interoperability among wide range of programs and environment, SOAP allows applications written in different languages and deployed on different platforms to communicate with each other over the network. While SOAP offers obvious benefits in the world of interoperability, it comes at a price of performance degradation and additional development efforts required for implementation of features missing from SOAP, such as security and state management. This paper reports the outcome of a comparative study of SOAP and DCOM in terms of features, development effort, and application performance. The results indicate that SOAP performance on a homogeneous platform is consistently worse than that of DCOM. Depending on the operation and the amount of data transferred, SOAP performance degradation can range from minor (e.g. two or three times slower than DCOM) to major (e.g. twenty or more times slower).

The Design and Implementation of an OpenGIS Conforming Feature-Coverage-Map Server Implementation Specification for CORBA

Two trends in geographic information science today are affecting Environmental Information Systems (EIS): standardization in Geographic Information Systems (GIS), and the application of middleware technology in heterogeneous computing environments. Research problems arise when the two trends meet each other in the EIS domain. In GIS, standardization is important for geospatial data sharing and geospatial service interoperation. The OpenGIS Consortium (OGC) published abstract specifications and partial implementation specifications, which can make diverse geospatial data and geospatial services accessible to conforming applications. For example, the OGC Simple Feature (SF) and Grid/Coverage (GC) geospatial data specifications specify the format and operations on geospatial feature (vector data) and coverage (raster data) as OpenGIS Simple Feature and Grid Coverage; the OGC Web Feature Server (WFS), Web Coverage Server (WCS), and Web Map Server (WMS) can publish and manage geospatial features, coverages, and maps via the Web. However the implementation specifications are still incomplete. With increasing applications of middleware technology, such as Common Object Request Broker Architecture (CORBA), Distributed Component Object Model (DCOM), and Java Remote Method Invocation (RMI), in GIS and EIS, it is necessary to design feature, coverage, and map server implementation specifications for CORBA, DCOM, and Java RMI. This paper presents an integrated feature-coverage-map server implementation specification for CORBA; similar to the OGC WFS, WCS, and WMS implementation specifications, it provides the access to features, coverages, and maps in a CORBA environment. Clients conforming to the implementation specification can interact with a CORBA feature-coverage-map server using the OpenGIS Simple Feature and Grid Coverage. An implementation based on the specification is also presented. The implementation transformed GRASS, an open source GIS, into a CORBA feature-coverage-map server. The evaluation results show that OpenGIS-based interoperability comes at an acceptable cost in terms of performance. The primary contributions of the paper are first that it presents an OpenGIS conforming feature-coverage-map server implementation specification for CORBA, and second that it presents a demonstration implementation and evaluates its performance.

Standards for talking computers [Book Review

Web Services recently emerged as the ideal choice for building distributed applications in heterogeneous environments where competing technologies (such as the Object Management Group's Corba, Microsoft's Distributed Component Object Model, or Sun's Java Remote Method Invocation) never really caught on. Web Services employ XML to facilitate communication in distributed heterogeneous systems. XML's easy-to-interpret format is perfect for building interoperable systems. In the unlikely case that an XML parser doesn't already exist in your programming environment, you can implement it in a breeze. Moreover, XML syntax is humanreadable-a highly desirable property for debugging sessions. In short, using XML simplifies computer-computer interaction so that distributed applications can more easily share data.

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.

E-Phys: a suite of intracellular neurophysiology programs integrating COM (Component Object Model) technologies

Current computer programs for intracellular recordings often lack advanced data management, are usually incompatible with other applications and are also difficult to adapt to new experiments. We have addressed these shortcomings in e-Phys, a suite of electrophysiology applications for intracellular recordings. The programs in e-Phys use Component Object Model (COM) technologies available in the Microsoft Windows operating system to provide enhanced data storage, increased interoperability between e-Phys and other COM-aware applications, and easy customization of data acquisition and analysis thanks to a script-based integrated programming environment. Data files are extensible, hierarchically organized and integrated in the Windows shell by using the Structured Storage technology. Data transfers to and from other programs are facilitated by implementing the ActiveX Automation standard and distributed COM (DCOM). ActiveX Scripting allows experimenters to write their own event-driven acquisition and analysis programs in the VBScript language from within e-Phys. Scripts can reuse components available from other programs on other machines to create distributed meta-applications. This paper describes the main features of e-Phys and how this package was used to determine the effect of the atypical antipsychotic drug clozapine on synaptic transmission at the neuromuscular junction.

DCOM 음성 모듈을 이용한 원격 대화식 학습 도구의 개발

본 논문에서는 WWW을 기반으로 한 게시판을 이용하여 교사와 학습자 사이에 질의 응답이 가능한 양방향 원격 대화식 학습 방법(RECT) 모듈을 개발하였다. RECT로 DCOM 음성 모듈을 이용하였는데 음성 자료의 사용은 교사에게 학습 자료 제작의 수월성을 주고, 학습자에게는 학습 환경을 준비하는데 수월성을 주기 위함이다. 게시판에서의 모든 학습 자료 및 질의 응답은 음성 모듈의 녹음 기능을 이용하여 음성 파일로 제공한다. 먼저 교사는 기본적인 설명을 게시판에 게시하고, 학생들은 교사의 설명을 들으면서 학습한다. 학생들이 교사의 설명으로 문제를 해결할 수 없을 때는 문제가 해결 될 때까지 교사에게 질문을 할 수 있고, 교사는 그에 대한 답변을 함으로써 양방향 원격 대화식 학습을 하고자 한다. This paper proposes Remote Educating Communication Tool (RECT) that allows students and teachers to communicate using Web-based Bulletin Board System. The distance teaching using DCOM (Distributed Component Object Model) voice module is used to enhance academic accomplishments for students in computer class. The DCOM voice module to be used in distance learning is designed, implemented and applied to teachers and students in the computer class in order to measure and analyze academic results. The RECT server provides Q&A sessions between students and teachers in the BBS using recording and playback functions. The client RECT includes recording and playback functions. The client module of RECT receives and uses DCOM module. When recording, the client transmits voice files with the recorded content to the server.

Effortless software interoperability with Jini* connection technology

Software components of mixed and uncertain provenance are the reality for large software systems. As such, getting these components to work together to form an integrated software product is vital, but it is made enormously complex by the aggregate system's uncontrolled heterogeneity. This paper focuses on a software integration strategy based on Sun Microsystems' Jini∗ connection technology. Jini had initially been promoted as a technology for interconnecting embedded devices. The ease with which we have been able to use it to accomplish software integration shows that software, whatever its size or age, is really just another “device.” We discuss the reasons why we opted for distributed object technology over other enterprise application integration (EAI) solutions and the advantages of Jini over other distributed object platforms such as Common Object Request Broker Architecture (CORBA∗) and Distributed Component Object Model (DCOM). We then describe techniques for achieving interoperability between CORBA and Jini and integrating generic “black-box” components. We also discuss the Dobos project, a Jini-based platform for building large distributed applications, and we close with examples showing how to use Dobos to integrate some historically stand-alone applications.

COPS: cooperative problem solving using DCOM

We present a framework that utilizes Distributed Component Object Model (DCOM) for distributed problem solving. The Cooperative Problem Solving (COPS) system provides for the coding and execution of a parallel algorithm by a number of networked computers running Microsoft Windows. We show the effectiveness of the COPS system by implementing parallel breadth-first search used in conjunction with a branch-and-bound algorithm for the Traveling Salesman Problem.

Integrating Building Management System and facilities management on the Internet

Recently, it is of great interest to adopt the Internet/Intranet to develop Building Management Systems (BMS) and Facilities Management Systems (FMS). This paper addresses two technical issues: the Web-based access (including database integration) and the integration of BMS and FMS. These should be addressed for accessing BMS remotely via Internet, integrating control networks using the Internet protocols and infrastructures, and using Internet/Intranet for building facilities management. An experimental Internet-enabled system that integrates Building and Facilities Management Systems has been developed and tested. This system integrated open control networks with the Internet and is developed utilizing the embedded Web server, the PC Web server and the Distributed Component Object Model (DCOM) software development technology on the platform of an open control network. Three strategies for interconnecting BMS local networks via Internet/Intranet are presented and analyzed.

Continuous media support in the distributed component object model

The demand for a great variety of sophisticated telecommunications services with multimedia characteristics is increasing. This trend highlights the need for the efficient creation of distributed programs with multimedia data exchanges running on distributed processing environments. Therefore, it is necessary to support the object-oriented development of distributed multimedia applications in a flexible manner. This paper recognises Microsoft's Distributed Component Object Model (DCOM) as a key potential technology in the area of service engineering and examines a structured approach to enhance it for the handling of continuous media streams through the design and implementation of a collection of suitable multimedia support services. The proposed approach focuses on the modelling of continuous media communications in DCOM and is validated through the design and implementation of a multimedia conferencing service. Though the approach is targeted to DCOM, the paper lays a set of concrete concepts for realising stream interfaces in distributed object platforms.

Flow measurement system model with distributed resources

The paper describes a general flow measurement system model with distributed resources based on Distributed Component Object Model (DCOM). Complex flow-rate calculation procedures are decomposed and distributed throughout the measurement system. The paper explains to what extent a flow measurement process can be partitioned into the services that can be realized as separate objects shareable across the network. Certain measurement system components perform local measurements and/or calculations and communicate with a remote measurement system resource via intranet/internet. The measurement system comprises direct measurements of the primary measurement quantities, the calculation of the flow-rate and the calculation of the physical properties for various gases, gas mixtures, water and steam. Using DCOM the measurement system automatically activates the remote client/server components that carry out flow-rate calculations in real time. The measurement system covers different measurement procedures and a variety of primary elements. The performances of the measurement system model have been verified by realizing a measurement system with two measuring sections.

Multi-technology distributed objects and their integration

Research on software objects, components, middleware, and component-based applications concerns among others ActiveX controls, JavaBeans (JBs), the Microsoft Transaction Server (MTS), Enterprise JavaBeans (EJBs), and how they can interoperate with each other. Is their interoperation possible? Which elements are responsible for the software objects' incompatibility? Is compatibility a responsibility of the objects or of their underlying architectures? In this article, we discuss object compatibility problems by outlining three basic middleware remoting technologies: the OMG's Common Object Request Broker Architecture (CORBA), Microsoft's Distributed Component Object Model (DCOM), and Sun's Java Remote Method Invocation (RMI), discussing the basic incompatibility points, and overviewing the basic strategies for bridging the gap between CORBA, DCOM, and RMI.

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.

Design and implementation of efficient communication abstractions on the Virtual Interface Architecture: Stream sockets and RPC experience

AbstractThe emergence and standardization of system area networks (SANs) has provided distributed applications with a medium for high‐bandwidth, low‐latency communication. Standard user‐level networking architecture such as the Virtual Interface (VI) Architecture enables distributed applications to perform low overhead communication over SANs. The VI Architecture significantly reduces system processing overheads and provides each consumer process with a protected, directly accessible interface to the network hardware. Developing distributed applications using low‐level primitives provided by user‐level networking architecture like the VI Architecture is complex and requires significant effort.This paper describes how high‐level communication paradigms like stream sockets and remote procedure call (RPC) can be efficiently built over the VI Architecture. To evaluate performance benefits for standard client–server and multi‐threaded environments, our focus is on off‐the‐shelf sockets and RPC interfaces and commercially available VI Architecture‐based SANs. The key design techniques developed in this paper include credit‐based flow control, decentralized user‐level protocol processing, caching of pinned communication buffers, and deferred processing of completed send operations.In the experimental evaluation, the one‐way bandwidth achieved by stream sockets over VI Architecture was three to four times better than the bandwidth achieved by running legacy protocols over the same interconnect. On the same SAN, high‐performance stream sockets and RPC over VI Architecture achieve significantly better (between 2× and 3× less) latency than conventional stream sockets and RPC over standard networking protocols in a Windows NT™ 4.0 environment. Furthermore, our high‐performance RPC transparently improved the network performance of the distributed component object model (DCOM) by a factor of two to three. Copyright © 2001 John Wiley & Sons, Ltd.