Interface groups and financial transfer architectures

Analytic execution architectures have been proposed by the same authors as a means to conceptualize the cooperation between heterogeneous collectives of components such as programs, threads, states and services. Interface groups have been proposed as a means to formalize interface information concerning analytic execution architectures. These concepts are adapted to organization architectures with a focus on financial transfers. Interface groups (and monoids) now provide a technique to combine interface elements into interfaces with the flexibility to distinguish between directions of flow dependent on entity naming. The main principle exploiting interface groups is that when composing a closed system of a collection of interacting components, the sum of their interfaces must vanish in the interface group modulo reflection. This certainly matters for financial transfer interfaces. As an example of this, we specify an interface group and within it some specific interfaces concerning the financial transfer architecture for a part of our local academic organization. Financial transfer interface groups arise as a special case of more general service architecture interfaces.Comment: 22 page

Object replication in a distributed system

PhD ThesisA number of techniques have been proposed for the construction of fault—tolerant applications. One of these techniques is to replicate vital system resources so that if one copy fails sufficient copies may still remain operational to allow the application to continue to function. Interactions with replicated resources are inherently more complex than non—replicated interactions, and hence some form of replication transparency is necessary. This may be achieved by employing replica consistency protocols to mask replica failures and maintain consistency of state between functioning replicas. To achieve consistency between replicas it is necessary to ensure that all replicas receive the same set of messages in the same order, despite failures at the senders and receivers. This can be accomplished by making use of order preserving reliable communication protocols. However, we shall show how it can be more efficient to use unordered reliable communication and to impose ordering at the application level, by making use of syntactic knowledge of the application. This thesis develops techniques for replicating objects: in general this is harder than replicating data, as objects (which can contain data) can contain calls on other objects. Handling replicated objects is essentially the same as handling replicated computations, and presents more problems than simply replicating data. We shall use the concept of the object to provide transparent replication to users: a user will interact with only a single object interface which hides the fact that the object is actually replicated. The main aspects of the replication scheme presented in this thesis have been fully implemented and tested. This includes the design and implementation of a replicated object invocation protocol and the algorithms which ensure that (replicated) atomic actions can manipulate replicated objects.Research Studentship, Science and Engineering Research Council. Esprit Project 2267 (Integrated Systems Architecture)

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

Suporte a grupo sobre a plataforma CORBA :: um estudo comparativo entre as abordagens /

Dissertação (Mestrado) - Universidade Federal de Santa Catarina, Centro Tecnológico

Gerenciamento de serviços de telecomunicações com CORBA e JAVA /

Dissertação (Mestrado) - Universidade Federal de Santa Catarina, Centro Tecnológico

Suporte a grupos cooperativos em ambiente distribuido aberto

Orientador: Edmundo Roberto Mauro MadeiraDissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Matematica, Estatistica e Ciencia da ComputaçãoResumo: O estilo de interação em grupo entre os usuários é característica básica de aplicações de trabalho cooperativo. Neste contexto, é fundamental a existência de suporte apropriado de sistemas distribuídos para a estruturação das aplicações em termos de grupos de objetos, permitindo a interação cooperativa entre eles. Este trabalho propõe um modelo para um serviço de suporte a grupos de objetos, a ser usado como ferramenta na construção de aplicações cooperativas. O modelo provê mecanismos para a manutenção consistente dos conjuntos de membros associados aos grupos, bem como para o suporte à coordenação e transparência da comunicação de grupo. A proposta fundamenta-se no Modelo de Referência para Processamento Distribuído Aberto da ISO (RM-ODP) e sua implementação utiliza os recursos da arquitetura CORBA (Common Object Request Broker Architecture), de forma a permitir o uso dos serviços em ambientes computacionais heterogêneos. O trabalho descreve a implementação de um protótipo, no ambiente da Plataforma Multiware, o qual provê os serviços básicos do modelo de suporte a grupos.Abstract: Computer supported cooperative work applications can be characterized by the style of group interactions among their users. In this context, it is essential the provision of mechanisms that offer suitable support to structure applications in terms of cooperating object groups. This work proposes a model of a group support service to be used as a tool for building cooperative applications. The model provides mechanisms to consistently maintain group membership, as well as to support the coordination and transparency of group communication. The work is based on the ISO Reference Model for Open Distributed Processing (RM-ODP) and its implementation uses resources from the Common Object Request Broker Architecture (CORBA), allowing the services to be used in a heterogeneous computing environment. It is also described the implementation of a prototype, in the Multiware Platform environment, which provides the basic services from the group support model.MestradoMestre em Ciência da Computaçã

Étude de l'invocation entre objets dupliqués dans un système réparti tolérant aux fautes

This dissertation studies the problems to solve in order to use the invocation paradigm to express replicated object communication in fault-tolerant distributed systems. The ultimate goal is to define abstractions which achieve replication encapsulation, ie which give the illusion that replication is an internal property of objects. Thus, object communication could be always expressed using the invocation paradigm, whether objects are replicated or not. Background The invocation paradigm defines a "request-reply" communication model which matches exactly the client-server model. The latter is generally used to express service interactions in distributed systems. For this reason, the object-oriented approach is well suited to the design of distributed system services. A service can be implemented as a set of objects, located on remote computers (or nodes). Service fault-tolerance is achieved by replicating the objects which implement the service. Most of the previous works about replicated objects consider only server object replication. This study is more general: both client and server can be replicated. Furthermore, replication policies of objects can be different. Four replication policies had been studied: active replication, passive replication, semi-active replication, and coordinator-cohort replication. Replication encapsulation Replication encapsulation means both plurality encapsulation and replication policy encapsulation. Plurality encapsulation consists in hiding from other objects, that a replicated object is actually a set of replicas located on several nodes. Replication policy encapsulation consists in hiding from other objects, the communication protocol to use in order to interact with object replicas without breaking their consistency. The symmetric invocation model Most of the related works are based on an asymmetric invocation model. In this model, the invocation reply follows exactly the reverse of the request communication path. The asymmetric invocation model can not be used to achieve replication encapsulation of client objects. This dissertation proposes a symmetric invocation model which solves this problem. The symmetric invocation model considers the request transmission and the reply transmission as two instances of the same problem: the transmission of a message to a replicated object. Both the analysis of the replication encapsulation problem and the symmetric invocation model were used to define a specification of replicated object invocation. This specification is a set of generic formal properties based on parameters which values depend on replication policies. The properties include object failure semantics which is expressed using the group paradigm and the view-synchronous communication paradigm. Every replicated object is built using an object group which membership changes whenever object replicas fail or restart. The N2M invocation service The main result of this study is the design1 of N2M, an invocation service which supports replicated objects. Objects using N2M are called application objects whereas objects implementing N2M are called communication objects. Communication objects take care of every aspect related to application object replication. Thus, replicated application objects communicate using regular invocations, just as if they were not replicated. There are actually two kinds of communication objects: encapsulators and mailers. Each replicated application object is built using an encapsulator group. Each application object replica is associated with a private encapsulator which acts as an invocation filter for this replica. To communicate with a replicated application object O, every object must interact with O's local mailer. On every node, a replicated application object is represented by a mailer which is responsible for transmitting requests and replies to the application object replicas. The originality of this model is its symmetry: there are both mailers of the server on the client nodes, and mailers of the client on the server nodes. This symmetry is directly inherited from the symmetric invocation model. Each replication policy is implemented using an encapsulator class and a mailer class. These classes replicate objects according to a specific replication policy, while respecting the invocation paradigm. In other words, communication object classes achieve replication encapsulation. The GARF-v2 programming environment The N2M service has been implemented in the context of the GARF project2. The GARF project aimed to provide a programming environment which faciltates the design of fault-tolerant distributed applications. The environment prototype was implemented in Smalltalk. It is based on the group communication layer provided by ISIS toolkit. ---------------------------------------   1this logo refers to the n to m expression which usually names the interaction between n client replicas and m server replicas.   2GARF is the french acronym for automatic generation of fault-tolerant applications