Distributed Object Architectures Research Articles

Improving availability and performance with application-specific data replication

The emerging edge services architecture promises to improve the availability and performance of Web services by replicating servers at geographically distributed sites. A key challenge in such systems is data replication and consistency, so that edge server code can manipulate shared data without suffering the availability and performance penalties that would be incurred by accessing a traditional centralized database. This work explores using a distributed object architecture to build an edge service data replication system for an e-commerce application, the TPC-W benchmark, which simulates an online bookstore. We take advantage of application-specific semantics to design distributed objects that each manages a specific subset of shared information using simple and effective consistency models. Our experimental results show that by slightly relaxing consistency within individual distributed objects, our application realizes both high availability and excellent performance. For example, in one experiment, we find that our object-based edge server system provides five times better response time over a traditional centralized cluster architecture and a factor of nine improvement over an edge service system that distributes code but retains a centralized database.

Formal verification and validation for e-commerce: theory and best practices

In this paper, we describe a formal, model-driven, CORBA-based approach to developing and testing e-commerce systems. We indicate advantages and limitations of formal verification techniques using the Specification and Description Language (SDL), and relate the CORBA-based distributed object architecture to standard test methods and TTCN, the international standard test language. Finally, we enumerate industrial challenges and best practices at one of the electronic commerce software test organizations in IBM, and suggest a strategy for adapting formal test methods to the evolving industrial e-commerce test process.

An artificial life approach for the animation of cognitive characters

This paper addresses the problem of cognitive character animation. We propose the use of finite state machines for the behavioral control of characters. Our approach rests on the idea that the cognitive character arises from the evolutionary computation embedded in the artificial life simulation, which in our case is implemented by the finite state machine. We present some of the results of the WOXBOT/ARENA research project. This project to build virtual worlds is aimed at the graphic simulation of an arena, where small mobile robots can perform requested tasks while behaving according to their own motivation and reasoning. Each robot is an intelligent agent that perceives the virtual environment through a simulated vision system and reacts by moving away from or approaching the object it sees. The conception and specification of the robots and environment are being done very carefully to create an open distributed object architecture that could serve as a test-bed freely available and ready to use for testing theories in some computational areas such as evolutionary computation, artificial life, pattern recognition, artificial intelligence, cognitive neurosciences and distributed objects architectures. Furthermore, it is a first step towards building a cognitive animated character.

A framework for designing ATM management systems by way of abstract information models and distributed object architectures

ATM network management has not yet reached the level of versatility and comprehensiveness exhibited by other aspects of this networking technology. Since the currently dominant general standards for broadband network management, primarily targeted towards large carrier networks, are too complex and intricate for smaller environments, e.g. LANs or corporate networks, ATM equipment manufacturers, in their effort to provide systems that exploit the power of ATM and yet remain practical and simple, usually resort to devising ad hoc proprietary extensions of simpler management frameworks, originally developed for other networking technologies. Such incompatible extensions, however, remain useless in the common case where the network is heterogeneous. The notion of abstract information modeling may be employed for improving on this situation.Building on this concept, the paper proposes a framework for developing ATM management systems intended for heterogeneous small- to medium-size networks. The general guidelines are illustrated through discussing a specific compliant management application intended for the remote monitoring of ATM network platforms and developed in the framework of a European research project. The application features a WWW interface and, as such, provides an example of the compatibility of information abstraction with the Web-based management techniques and of the benefits arising from the combination of the two notions.Lastly, and as the concept of abstracting information is inherent to recent frameworks for designing and programming distributed object systems, the paper explores this relation by discussing an alternative design of the monitoring application as a distributed object system.

Supporting parallel computing on a distributed object architecture

The availability of high-speed networks and increasingly powerful commodity microprocessors is making the usage of clusters, or networks, of computers an appealing platform for cost effective parallel computing. However, the ease of developing efficient high-performance parallel software to exploit these platforms presents a major challenge. Advances in distributed object software technology have made the management of distributed computing resources easier than before. This also brings many benefits for parallel computing. Firstly, distributed object technology facilitates the encapsulating of parallel computing resources into a uniform model despite their differences in implementations that are based on different languages executing on different platforms. Secondly, mature object-oriented analysis, design method, as well as component idea embodied in distributed object technology can enhance the reusability of parallel software. To support parallel computing in a distributed object-based computing platform, a uniform high performance distributed object architecture layer is necessary. In this paper, we propose a distributed object-based framework called DoHPC to support parallel computing on distributed object architectures. We present the use of dependence analysis technique to exploit intra-object parallelism and an interoperability model for supporting distributed parallel objects. Experimental results on a Fujitsu AP3000 workstation cluster consisting of a cluster of 32 UltraSPARC workstations show that the implementation of inter-object parallelism on a workstation cluster environment is efficient. With intra-object parallel computation speedup efficiency is greater than 90% and with overhead of less than 10% for large problem, and the interoperability model improves speedup by 20%.

Performance comparison of CORBA and RMI

Distributed object architectures and Java are important for building modern, scalable, web-enabled applications. This paper is focused on qualitative and quantitative comparison of two distributed object models for use with Java: CORBA and RMI. We compare both models in terms of features, ease of development and performance. We present performance results based on real world scenarios that include single client and multi-client configurations, different data types and data sizes. We evaluate multithreading strategies and analyse code in order to identify the most time-consuming methods. We compare the results and give hints and conclusions. We have found that because of its complexity CORBA is slightly slower than RMI in simple scenarios. On the other hand, CORBA handles multiple simultaneous clients and larger data amounts better and suffers from far lower performance degradation under heavy client load. The article presents a solid basis for making a decision about the underlying distributed object model.

Integrating legacy systems in distributed object architecture

The ability of a new technology to reuse legacy systems is very important for its economic success. This paper presents a method for integrating legacy systems within distributed object architectures. The necessary steps required for integration are defined. It is explained how to define object interfaces. A detailed overview of how to implement the wrappers is given. The paper also answers the question which distributed object model is most suitable for legacy integration. Therefore a decision model is defined and the evaluation results are presented.

Predicting the behaviour of three-tiered applications: dealing with distributed-object technology and databases

Today’s applications are both object-oriented and based on a new type of three-tiered client–server architecture with clients, processing servers, and data servers as cornerstones. By recognising these trends, industry and researchers have been engaged in defining standards and technologies for communicating the components of Distributed Information Systems and for providing compatible mechanisms to access databases, but a key problem with these complex architectures is still their performance. This paper presents a tool for predicting the performance of systems based on CORBA and DCOM as distributed-object architectures, and OLE-DB and PL/SQL as data-access architectures. The tool is an extension of SMART, a workbench that exploits analytical and simulation performance models to predict the performance of database applications.

An Internet‐based framework for federated process support

The coupling of process‐centered environments (PCEs) with distributed object architectures like COM, CORBA and Java opens up an unprecedented range of possibilities in terms of automatic process management. The human factor is still the major component of the software process but its role is changing, as is the kind of support it needs. Focusing on the interactions between different distributed PCEs (heterogeneous federation), we present an Internet‐based framework for the definition and enactment of federated processes. A CSP‐like process definition language makes distribution problems transparent to the process designer while compiler and execution engines exploit Internet technology in order to map process specifications into the actual IT infrastructure. Different solutions are investigated for both the deployment of the enactment components and their interaction with local PCEs.

Java and distributed object models

Java has an important role in building distributed object oriented web enabled applications. In the article an analysis of two distributed object models in context of Java language is presented. Several aspects of RMI and CORBA such as features, maturity, support for legacy systems, learning curve and ease of development are compared. A special emphasis is given to the performances. Different testing scenarios give a complete overview about real world performances of both architectures. Based on the comparison results, recommendations for selecting the most appropriate architecture for a given problem domain are presented. Therefore the paper contributes to the understanding of the distributed object architectures and to the study of Java RMI and CORBA performances.

Towards a richer Web object model

The World Wide Web is becoming an increasingly important factor in planning for enterprise distributed computing environments, both to support external access to enterprise systems and information (e.g., by customers, suppliers, and partners), and to support internal enterprise operations. Organizations perceive a number of advantages in using the Web in enterprise computing, a particular advantage being that it provides an information representation which• supports interlinking of all kinds of content• is easy for end-users to access• supports easy content creation using widely-available toolsHowever, as organizations have attempted to employ the Web in increasingly sophisticated applications, these applications have begun to overlap in complexity the sorts of distributed applications for which distributed object architectures such as OMG's CORBA, and its surrounding Object Management Architecture (OMA) [Sol95] were originally developed. Since the Web was not originally designed to support such applications, Web application development efforts increasingly run into limitations of the basic Web infrastructure.If the Web is to be used as the basis of complex enterprise applications, it must provide generic capabilities similar to those provided by the OMA (although these may need to be adapted to the more open, flexible nature of the Web, and specific requirements of Web applications). This involves such things as providing database-like services (such as enhanced query and transaction support) and their composition in the Web. However, the basic data structuring capabilities provided by the Web (its "object model") must also be addressed, since the ability to define and apply powerful generic services in the Web, and the ability to generally use the Web to support complex applications, depends crucially on the ability of the Web's underlying data structuring facilities to support these complex applications and services.

Panel session on component software

Component software and distributed object architectures are receiving considerable attention at the moment. With HEP experiments increasing in size and complexity shouldn't the physics community look to adopt this technology? But what is component software, what are the potential benefits and disadvantages? Can quality components be bought off the shelf? Which components models are best? Is the technology mature enough? Perhaps physicists should be actively involved in the standards making process to produce common facility components for HEP experiments and accelerators? This panel session aims to answer some of these questions and provide feedback of experiences gained in using this technology.

The promise of distributed business components

This paper discusses the advantages of replacing hand-crafted software with reusable components as a solution to the software crisis. Object-oriented programming provides insights on how to build components. Because components must have distributed implementations and well-defined interfaces, both the Microsoft Component Object Model (COM) and the Object Management Group (OMG) Common Object Request Broker Architecture (CORBA) models are described as distributed object architectures to support reusable components. A transaction processing monitor is also necessary for accessing business logic and the information contained in relational databases. Components are composed of object-oriented frameworks based on models of the problem domain or business.