An architectural comparison of distributed object technologies

Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1997.Includes bibliographical references (p. 115-117).by Jay Ongg.M.Eng

Adaptive object management for distributed systems

This thesis describes an architecture supporting the management of pluggable software components and evaluates it against the requirement for an enterprise integration platform for the manufacturing and petrochemical industries. In a distributed environment, we need mechanisms to manage objects and their interactions. At the least, we must be able to create objects in different processes on different nodes; we must be able to link them together so that they can pass messages to each other across the network; and we must deliver their messages in a timely and reliable manner. Object based environments which support these services already exist, for example ANSAware(ANSA, 1989), DEC's Objectbroker(ACA,1992), Iona's Orbix(Orbix,1994)Yet such environments provide limited support for composing applications from pluggable components. Pluggability is the ability to install and configure a component into an environment dynamically when the component is used, without specifying static dependencies between components when they are produced. Pluggability is supported to a degree by dynamic binding. Components may be programmed to import references to other components and to explore their interfaces at runtime, without using static type dependencies. Yet thus overloads the component with the responsibility to explore bindings. What is still generally missing is an efficient general-purpose binding model for managing bindings between independently produced components. In addition, existing environments provide no clear strategy for dealing with fine grained objects. The overhead of runtime binding and remote messaging will severely reduce performance where there are a lot of objects with complex patterns of interaction. We need an adaptive approach to managing configurations of pluggable components according to the needs and constraints of the environment. Management is made difficult by embedding bindings in component implementations and by relying on strong typing as the only means of verifying and validating bindings. To solve these problems we have built a set of configuration tools on top of an existing distributed support environment. Specification tools facilitate the construction of independent pluggable components. Visual composition tools facilitate the configuration of components into applications and the verification of composite behaviours. A configuration model is constructed which maintains the environmental state. Adaptive management is made possible by changing the management policy according to this state. Such policy changes affect the location of objects, their bindings, and the choice of messaging system

A semi-formal comparison between the Common Object Request Broker Architecture (COBRA) and the Distributed Component Object Model (DCOM)

The way in which application systems and software are built has changed dramatically over the past few years. This is mainly due to advances in hardware technology, programming languages, as well as the requirement to build better software application systems in less time. The importance of mondial (worldwide) communication between systems is also growing exponentially. People are using network-based applications daily, communicating not only locally, but also globally. The Internet, the global network, therefore plays a significant role in the development of new software. Distributed object computing is one of the computing paradigms that promise to solve the need to develop clienVserver application systems, communicating over heterogeneous environments. This study, of limited scope, concentrates on one crucial element without which distributed object computing cannot be implemented. This element is the communication software, also called middleware, which allows objects situated on different hardware platforms to communicate over a network. Two of the most important middleware standards for distributed object computing today are the Common Object Request Broker Architecture (CORBA) from the Object Management Group, and the Distributed Component Object Model (DCOM) from Microsoft Corporation. Each of these standards is implemented in commercially available products, allowing distributed objects to communicate over heterogeneous networks. In studying each of the middleware standards, a formal way of comparing CORBA and DCOM is presented, namely meta-modelling. For each of these two distributed object infrastructures (middleware), meta-models are constructed. Based on this uniform and unbiased approach, a comparison of the two distributed object infrastructures is then performed. The results are given as a set of tables in which the differences and similarities of each distributed object infrastructure are exhibited. By adopting this approach, errors caused by misunderstanding or misinterpretation are minimised. Consequently, an accurate and unbiased comparison between CORBA and DCOM is made possible, which constitutes the main aim of this dissertation.ComputingM. Sc. (Computer Science

Un modelo de mediación para el desarrollo de software basado en componentes COTS

Aunque realmente es muy complicado predecir y cuantificar el impacto que podría tener en un futuro la utilización de las prácticas de desarrollo basadas en componentes COTS en las organizaciones, sí que puede cambiar la forma de pensar de los ingenieros a la hora de afrontar sus proyectos, ya que este planteamiento está haciendo que la ingeniería del software se enfrente a nuevos estilos de desarrollo de software, ascendentes y siguiendo algún modelo en espiral (como el de Nuseibeh, 2001), frente al desarrollo tradicional, descendente y en cascada. Una de las principales consecuencias de este estilo de desarrollo (ascendente y basado en componentes comerciales) es el acercamiento fehaciente de tres áreas importantes de la Ingeniería del software, como son las arquitecturas de software, los servicios de mediación y las especificaciones de componentes. Este acercamiento ha venido propiciado por la inherente naturaleza del estilo de desarrollo ascendente: la necesidad de contemplar sistemáticamente las características de implementación de los componentes en fases de diseño del sistema. Una de las principales motivaciones del presente trabajo ha sido la de tratar de acercar aún más estas tres áreas de la ingeniería del software con la intención de ofrecer una propuesta de solución al problema de la conexión diseño-implementación, anteriormente citado. Por tanto, el trabajo aquí presentado ofrece sus contribuciones dentro del paradigma del desarrollo de software basado en componentes, y en particular en los campos de (a) los componentes comerciales, (b) los modelos de mediación y (c) los modelos de documentación de componentes, en donde su principal aportación es la definición de un modelo de mediación de componentes COTS para la construcción de aplicaciones de software en entornos abiertos y distribuidos. Las principales aportaciones de este trabajo son las siguientes: Se ha realizado un estudio de la actual función de mediación de ODP y se han identificado una serie de limitaciones para trabajar con componentes comerciales. Este estudio ha sido clave para el diseño posterior de un modelo de mediación para componentes COTS. Se define un modelo de mediación de componentes diseñado para construir aplicaciones de software a partir de componentes comerciales. A partir de este modelo se ha desarrollado una implementación de un servicio de mediación, denominado COTStrader. También se define un modelo para la documentación de componentes COTS, y un lenguaje en la notación XMLSchemas (W3C) que lo sustenta. Este lenguaje permite definir especificaciones de componentes comerciales en plantillas XML, denominadas COTScomponent. También, se estudia y ofrece una solución a ciertos problemas que aparecen en la construcción de aplicaciones de software cuando se combinan especificaciones de componentes con múltiples interfaces: los problemas de las lagunas y solapamientos entre interfaces. También se extienden los tradicionales operadores de reemplazabilidad y compatibilidad de componentes para el caso de múltiples interfaces, y se define un algoritmo de configuración que utiliza estos operadores extendidos para calcular la lista de combinaciones de especificaciones de componente a partir de una colección de componentes candidatos dada. Se ha desarrollado una implementación del algoritmo de configuración, denominado COTSconfig. Para definir una arquitectura de software con información de componentes COTS, se realiza una propuesta que utiliza la notación UML-RT extendiendo las representaciones gráficas de las cápsulas mediante notas, estereotipos y valores etiquetados, para modelar la captura de los requisitos de los componentes del sistema. Se ha definido un método de desarrollo de software semi-automatizado para la construcción de aplicaciones con componentes comerciales, y que pone de manifiesto cómo se pueden integrar nuestras propuestas en algunos tipos de metodologías en espiral del DSBC. Se ha desarrollado un caso ejemplo completo de una aplicación de software con componentes comerciales, en el campo de los sistemas de información geográficos (SIG)

Integrating ObjectBroker and DCE Security The integration of the ObjectBroker software product with the Distributed Computing Environment (DCE) Security Service makes

ObjectBroker the most secure object request broker (ORB) in the industry. ObjectBroker and DCE Security together allow client-to-server, server-to-client, and mutual authentication. The integrated software provides these security functions, as well as message integrity protection, transparently to the applications. Integration has been accomplished in a way that allows plug-in replacement of the ObjectBroker security subsystem by DCE Security, Kerberos, or any thirdparty software security product that supports the DCE’s Generic Security Service Application Programming Interface (GSS-API). This approach supports future GSS-API–compliant third-party security products based on Kerberos and also products that may address other security technologies such as biometrics and smart cards. In addition, the approach places responsibility for compliance with International Traffic in Arms Regulations in the hands of the purveyors and owners of GSS libraries rather than with the ORB vendor. Note that the ObjectBroker product is middleware jointly developed and distributed by DIGITAL and BEA Systems, who have formed a worldwide technology and distribution partnership. 42 Digital Technical Journal Vol. 9 No. 1 199