<title>MIRage: integration of heterogeneous distributed image database systems by object request broker</title>

One of the most attractive aspects of the Common Object Request Broker Architecture (CORBA) lies in its open standard nature. Code that is based only on constructs described in the CORBA specification is portable between object request brokers (ORBs) without depending on any single ORB implementation. However, this portability feature is not completely achieved in real-world applications. This paper discusses CORBA portability issues through our experience in implementing a CORBA object group service (OGS) and porting it on different ORBs. In particular, we discuss some implementation choices we made with Orbix and VisiBroker, and we point out the impact of these choices on the service portability and interoperability. This sheds some light on whether the current CORBA specification is mature enough to be deployed in industrial systems that have requirements regarding portability and interoperability. We also present how new CORBA specifications solve part of the shortcomings mentioned in this paper.

Problem statement: This study presents an in-depth analysis of the performance of Software Communications Architecture (SCA) component-based waveform applications in terms of inter-component communications. The main limitation with SCA, in the context of embedded systems, is the additional cost introduced by the use of Object Request Broker (ORB) middleware. The ORB middleware handles the interaction between components and objects in SCA distributed environment. This interaction should be highly efficient, due to the real time nature of SCA systems and transparent to the application programmer. Approach: We can achieve high efficiency in SCA systems by enhancing the Inter-Process Communications (IPC) mechanisms in Operating systems (OS) micro kernels, while we achieve transparency through Interface Definition Language (IDL). Different encoding mechanisms like “External Data Representation (XDR), Network Data Representation (NDR) and Common Data Representation (CDR) facilitate inter-component communication transparently and efficiently”. Marshalling procedures format data from the local machine representation to common network representations. A most common encoding mechanism for Common Object Request Broker Architecture (CORBA) systems is CDR representation. Measurements have been performed with ORBExpress DSP as a CORBA distribution and Open Source SCA Implementation Embedded (OSSIE) for SCA implementation. In order to perform these measurements we proposed two metrics for profiling the ORB that are invocation and marshalling. In addition, we propose three elements of data types to evaluate the performance of ORB middleware that are, Basic, Array and Sequence data types. Results: The CORBA bus is really the part, which brings an overhead to the SCA radio systems. This overhead is due to method invocations that have been carried out by ORB middleware. Conclusion: Performance benchmarks of ORBExpress DSP middleware show that, although using CORBA for inter-component communications introduces delays and overheads, the overall effect can be reduced by sending packets of data instead of basic data type elements.

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.

Coexistence of a great number of various heterogeneous-configured information systems due to characteristics of trans-regional and grouping enterprises has resulted in great difficulty in information interaction and interoperability among the enterprises' systems. So it is an urgent challenge that a breakthrough should be made with the regional constraint on the enterprise's information system for seamless integration and information resources sharing. This paper first describes the traditional application integration solution based on Common Object Request Broker Architecture (CORBA) and Distributed Component Object Model (DCOM) which has the shortcomings of close coupling and constrains imposed by the developer firms, then proposes an operation mode of the printing factory-centered virtual printing-enterprise based on the Service-Oriented Architecture (SOA) and Web service technologies. With the detail analysis of the application integration framework building of the virtual printing-enterprise, the corresponding realization methods are presented. Finally, a case of application integration is presented to demonstrate the methods' feasibility and effectiveness in accomplishing application integration of virtual printing-enterprise.

A framework for the distribution of program objects in heterogeneous computer systems using Common Object Request Broker Architecture (CORBA) is described. Any load balancing algorithm can be integrated transparently into the existing CORBA infrastructure. The implementation was tested with different load balancing strategies on an algorithm performing an exhaustive search over all possible paths, over all interconnection topologies of n nodes. The goal is to find the topology yielding the minimal sum of average and maximal distances among all pairs of nodes in minimal execution time.

Distributed computing applications rely on transmissions of messages between processes. However, as workstations are not intended to manage this kind of communications, it is necessary to use some communication tools known as message passing libraries. Currently, MPI (Message Passing Interface) and PVM (Parallel Virtual Machine) are the most used. In addition, the need for interoperability among the rapidly proliferating amount of hardware and software led to the definition of CORBA (Common Object Request Broker Architecture), which standardizes the execution support of distributed object applications. This architecture offers good interoperability and encapsulation support. Moreover, its method invocation mechanism, offers several features and can be used as a good communication model. Consequently, the use of such an architecture for distributed and grid computing applications seems interesting and promising. However, CORBA is always criticized on the performance level. By taking account of all these elements, a performance evaluation of CORBA seems necessary. The aim of the paper is to present benchmark results of some CORBA implementations (ORBacus and TAO) and to compare them with those of the two message passing libraries MPI (MPICH and LAM) and PVM, by using a Network of WorkStations (NOW).

For many applications such as command and control, telecommunications, and process control, it is critical that they meet timing constraints and ensure predictable computation. Furthermore, some of these applications are also distributed in nature and utilize distributed object management technology such as object request brokers (ORB) for interoperability. Therefore, it is necessary to integrate real time systems technology with distributed object management technology for many distributed real time applications. The article describes some of the issues that need to be investigated in order to develop real time data processing extensions to the common object request broker architecture (CORBA). In particular, issues on extensions to ORBs are given. A discussion of some real time services and applications hosted on real time ORBs is also provided. Finally, an overview of the work of the Object Management Group's Real time Special Interest Group is provided.

This chapter introduces a programming environment for SCI clusters that takes advantage of both parallel and distributed programming paradigms. It aims at helping programmers to design high performance applications based on the assembling of generic software components. This environment is based on CORBA (Common Object Request Broker Architecture), with our own extensions to support parallelism across several cluster nodes within a distributed system. Our contribution concerns extensions to support a new kind of object, which we call a parallel CORBA object (or parallel object), as well as the integration of message-passing paradigms, mainly MPI, within a parallel object. These extensions exploit as much as possible the functionality offered by CORBA and require few modifications to an available CORBA implementation. This paper reports on these extensions and the description of a runtime system, called Cobra, which provides resource allocation services for the execution of parallel objects.

The robot middleware is a key concept in developing complex robot systems even in geographically distributed environment. Giving a handy API, reusable standardized components and communication channels together with some automatism, the robot middleware helps the user to build easily reconfigurable systems. The behavior of the components and the manner of interaction among them are standardized by the Robotic Technology Component (RTC) specification. One implementation of the RTC specification is the OpenRTM-aist. It is a well written and convenient modular system built upon the Common Object Request Broker Architecture (CORBA). The first version of CORBA is released in 1991. Nowadays the CORBA is getting more and more out of date. Our ultimate goal is developing a new robot middleware in which we apply a modern distributed framework instead of CORBA. As a first step of the substitution we suggest some practical extensions of the OpenRTM-aist by the adaptation of the Internet Communication Engine (ICE) for component communication and the introduction of the web application concept for system editing and control. Having these structural modifications the resulting system became more powerful than the original system has been. The chapter introduces some structural and implementation details of the OpenRTM-aist together with the results of the experiments done for the performance comparison of the original and extended system.

Robot systems are comprised of several elements working together as a whole. The specific task of the robot system determines which elements are required. These reusable, fungible elements can be implemented as components which connect each other via communication channels and well-defined interfaces. The behavior of the components and the manner of interaction among them can be standardized by the Robotic Technology Component (RTC) specification. One promising implementation of the RTC specification called OpenRTM-aist is a software platform assisting to the component-oriented robot system development. In OpenRTM-aist both the specification and the implementation is based on the Common Object Request Broker Architecture (CORBA) and its remote method invocation. The first version of CORBA was released in 1991. In spite of the updates CORBA is getting more and more out of date. Several solutions exist which can replace or extend CORBA. Our ultimate goal is replacing the CORBA and setting up a modern distributed robot system development framework which is based on the original OpenRTM-aist specification. To be the first step of this task in this paper we suggest some practical extensions of the existing OpenRTM-aist robot middleware. These modifications are the adaptation of the Internet Communication Engine (ICE) for inter-component communication and as a new scheme, the introduction of the web application concept. After these structural modifications the resulting system became more powerful, and thanks to the web application concept much more user friendly.

The National Solar Observatory is nearing completion of the Synoptic Optical Long-term Investigations of the Sun (SOLIS) project. SOLIS will replace the existing capabilities of the Vacuum Telescope on Kitt Peak near Tucson, Arizona and will provide new scientific capabilities over its expected 25 year life-time. The evolution of the Common Object Request Broker Architecture (CORBA) and the availability of compliant Object Request Brokers (ORBs) and Common Object Services (COS) facilitates the development of cross-platform, multi-language software systems that are reliable and flexible. The SOLIS Communications System employs three ORBs, a naming service and a notification service to support the project's core distributed and real-time control systems that are written primarily in Java or C++ for the Linux, Solaris and VxWorks operating systems. One particularly useful aspect of the communications system is the ease of event monitoring demonstrated by the development of tools such as a logging service and a generic instrument control graphical user interface.

Intelligent Internet Computing (IIC) is emerging rapidly including grid, cluster computing, and peer-topeer computing to provide computing and communication services any time and anywhere. IIC foresees the integration of communicating and computational devices and applications in our heterogeneous computing environments. In this paper, we focus on the task allocation, which is a typical problem in the area of high performance computing and has been extensively studied in the past. Efficient task allocation is critical for achieving secure and high performance in a heterogeneous computing (HC) environment. In addition, the problem of allocating these tasks to the machines of a HC environment has been shown, in general, to be NP-complete, requiring the development of heuristic techniques. Therefore, a task allocation algorithm based on discrete particle swarm optimization (PSO) algorithm in the HC environment is proposed in this paper. Firstly, a new structure of cluster system is designed, and a mathematical model is built for dynamic server alliance according to practical tasks and situations of servers. Then an efficient discrete PSO with a well-designed particle position code and fitness function is proposed. A mutation operator which can effectively improve the algorithm's ability of global search and population diversity is also introduced in this algorithm. Finally, the simulation results compared with other algorithms show that this proposed algorithm produces better results in terms of both quality of solution and convergence speed.

In recent years there has been an increasing interest in object-oriented distributed computing since it is better equipped to deal with complex systems while providing extensibility, maintainability and reusability. At the same time, several new high-speed network technologies have emerged for local and wide area networks. However, the performance of networking software is not improving as fast as the networking hardware and the workstation microprocessors. This paper gives an overview and evaluates the performance of the Common Object Request Broker Architecture (CORBA) standard in a distributed computing environment at NASA Ames Research Center. The environment consists of two testbeds of SGI workstations connected by four networks: Ethernet, FDDI, HiPPI and ATM. The performance results for three communication software systems are presented, analysed and compared. These systems are: BSD socket programming interface, IONA's Orbix, an implementation of the CORBA specification and the PVM message passing library. The results show that high-level communication interfaces, such as CORBA and PVM, can achieve reasonable performance under certain conditions.

Designing with the 68008 microprocessor: Barth, A JWireless World Vol 90 No 1579 (April 1984) p 30

The use of component architectures to solve the problem of reuse and interoperability in scientific computing has been investigated by various research groups during the last years. Moreover, architectures for Internet accessible mathematical services have been proposed. In this paper we give a brief abstract requirements analysis with respect to these problems and show that there is an existing technology that solves most of the requirements. The Common Object Request Broker Architecture (CORBA) provides a component framework that can be used for Internet accessible mathematical services and also for the efficient reuse of medium grained size functionality. We give some examples on the use of CORBA with respect to both applications. We provide measurement data which show that components of a granularity of less than {100} ms can be reused with an acceptibly small overhead.