Describes an approach to building a distributed software component system for scientific and engineering applications that is based on representing Computational Grid services as application-level software components. These Grid services provide tools such as registry and directory services, event services and remote component creation. While a service-based architecture for grids and other distributed systems is not new, this framework provides several unique features. First, the public interfaces to each software component are described as XML documents. This allows many adaptors and user interfaces to be generated from the specification dynamically. Second, this system is designed to exploit the resources of existing Grid infrastructures like Globus and Legion, and commercial Internet frameworks like e-speak. Third, and most important, the component-based design extends throughout the system. Hence, tools such as application builders, which allow users to select components, start them on remote resources, and connect and execute them, are also interchangeable software components. Consequently, it is possible to build distributed applications using a graphical "drag-and-drop" interface, a Web-based interface, a scripting language like Python, or an existing tool such as Matlab.

Development of high-performance distributed applications can be extremely challenging because of their complex runtime environment coupled with their requirement of high-performance. Such applications typically run on a set of heterogeneous machines with dynamically varying loads, connected by heterogeneous networks possibly supporting a wide variety of communication protocols. In spite of the size and complexity of such applications, they must provide the required high-performance mandated by their users. In order to achieve this goal, they need to adaptively utilize their computational and communication resources. The paper describes EMOP: a programming environment for building high-performance distributed systems. EMOP is designed on the lines of CORBA and uses an Object Request Broker (ORB) to support seamless communication between distributed application components. In order to provide adaptive utilization of communication resources, it uses the principle of open implementation to open up the communication mechanisms of its ORB. By virtue of its open architecture, the ORB supports multiple, possibly custom, communication protocols, along with automatic and user controlled protocol selection at run-time. In order to support adaptive utilization of computational resources, EMOP also provides a flexible and powerful set of load-balancing mechanisms that can be used to implement custom load-balancing strategies. The paper describes EMOP's Open ORB architecture and load balancing mechanisms, and uses a set of simple experiments to demonstrate their usefulness.

Java RMI provides an elegant and powerful model for invoking member functions on objects that exist in remote address spaces. Unfortunately, it is a Java-to-Java communication model, and in many of the scientific applications we would like Java objects to interact with modules written in C++ or Fortran. This paper explores the design of RMI and extracts a subset of the RMI object model that is compatible with C++ and HPC++ remote object semantics. This RMI subset has been implemented to run over the Nexus runtime system and is being used as part of the LSA distributed linear system analyzer project. © 1998 John Wiley & Sons, Ltd.