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

Domain architecture a design framework for system development and integration

The ever growing complexity of software systems has revealed many short-comings in existing software engineering practices and has raised interest in architecture-driven software development. A system\u27s architecture provides a model of the system that suppresses implementation detail, allowing the architects to concentrate on the analysis and decisions that are most critical to structuring the system to satisfy its requirements. Recently, interests of researchers and practi-tioners have shifted from individual system architectures to architectures for classes of software systems which provide more general, reusable solutions to the issues of overall system organization, interoperability, and allocation of services to system components. These generic architectures, such as product line architectures and domain architectures, promote reuse and interoperability, and create a basis for cost effective construction of high-quality systems. Our focus in this dissertation is on domain architectures as a means of development and integration of large-scale, domain-specific business software systems. Business imperatives, including flexibility, productivity, quality, and ability to adapt to changes, have fostered demands for flexible, coherent and enterprise--wide integrated business systems. The components of such systems, developed separately or purchased off the shelf, need to cohesively form an overall compu-tational environment for the business. The inevitable complexity of such integrated solutions and the highly-demanding process of their construction, management, and evolution support require new software engineering methodologies and tools. Domain architectures, prescribing the organization of software systems in a business domain, hold a promise to serve as a foundation on which such integrated business systems can be effectively constructed. To meet the above expectations, software architectures must be properly defined, represented, and applied, which requires suitable methodologies as well as process and tool support. Despite research efforts, however, state-of-the-art methods and tools for architecture-based system development do not yet meet the practical needs of system developers. The primary focus of this dissertation is on developing methods and tools to support domain architecture engineering and on leveraging architectures to achieve improved system development and integration in presence of increased complexity. In particular, the thesis explores issues related to the following three aspects of software technology: system complexity and software architectures as tools to alleviate complexity; domain architectures as frameworks for construction of large scale, flexible, enterprise-wide software systems; and architectural models and representation techniques as a basis for good” design. The thesis presents an archi-tectural taxonomy to help categorize and better understand architectural efforts. Furthermore, it clarifies the purpose of domain architectures and characterizes them in detail. To support the definition and application of domain architectures we have developed a method for domain architecture engineering and representation: GARM-ASPECT. GARM, the Generic Architecture Reference Model, underlying the method, is a system of modeling abstractions, relations and recommendations for building representations of reference software architectures. The model\u27s focus on reference and domain architectures determines its main distinguishing features: multiple views of architectural elements, a separate rule system to express constraints on architecture element types, and annotations such as “libraries” of patterns and “logs” of guidelines. ASPECT is an architecture description language based on GARM. It provides a normalized vocabulary for representing the skeleton of an architecture, its structural view, and establishes a framework for capturing archi-tectural constraints. It also allows extensions of the structural view with auxiliary information, such as behavior or quality specifications. In this respect, ASPECT provides facilities for establishing relationships among different specifications and gluing them together within an overall architectural description. This design allows flexibility and adaptability of the methodology to the specifics of a domain or a family of systems. ASPECT supports the representation of reference architectures as well as individual system architectures. The practical applicability of this method has been tested through a case study in an industrial setting. The approach to architecture engineering and representation, presented in this dissertation, is pragmatic and oriented towards software practitioners. GARM-ASPECT, as well as the taxonomy of architectures are of use to architects, system planners and system engineers. Beyond these practical contributions, this thesis also creates a more solid basis for expbring the applicability of architectural abstractions, the practicality of representation approaches, and the changes required to the devel-opment process in order to achieve the benefits from an architecture-driven software technology

Dynamic Assembly for System Adaptability, Dependability, and Assurance

(DASASA) ProjectAuthor-contributed print ite

Integrating legacy mainframe systems: architectural issues and solutions

For more than 30 years, mainframe computers have been the backbone of computing systems throughout the world. Even today it is estimated that some 80% of the worlds' data is held on such machines. However, new business requirements and pressure from evolving technologies, such as the Internet is pushing these existing systems to their limits and they are reaching breaking point. The Banking and Financial Sectors in particular have been relying on mainframes for the longest time to do their business and as a result it is they that feel these pressures the most. In recent years there have been various solutions for enabling a re-engineering of these legacy systems. It quickly became clear that to completely rewrite them was not possible so various integration strategies emerged. Out of these new integration strategies, the CORBA standard by the Object Management Group emerged as the strongest, providing a standards based solution that enabled the mainframe applications become a peer in a distributed computing environment. However, the requirements did not stop there. The mainframe systems were reliable, secure, scalable and fast, so any integration strategy had to ensure that the new distributed systems did not lose any of these benefits. Various patterns or general solutions to the problem of meeting these requirements have arisen and this research looks at applying some of these patterns to mainframe based CORBA applications. The purpose of this research is to examine some of the issues involved with making mainframebased legacy applications inter-operate with newer Object Oriented Technologies

PRODUCT LINE ARCHITECTURE FOR HADRONTHERAPY CONTROL SYSTEM: APPLICATIONS DEVELOPMENT AND CERTIFICATION

Hadrontherapy is the treatment of cancer with charged ion beams. As the charged ion beams used in hadrontherapy are required to be accelerated to very large energies, the particle accelerators used in this treatment are complex and composed of several sub-systems. As a result, control systems are employed for the supervision and control of these accelerators. Currently, The Italian National Hadrontherapy Facility (CNAO) has the objective of modernizing one of the software environments of its control system. Such a project would allow for the integration of new types of devices into the control system, such as mobile devices, as well as introducing newer technologies into the environment. In order to achieve this, this work began with the requirement analysis and definition of a product line architecture for applications of the upgraded control system environment. The product line architecture focuses on reliability, maintainability, and ease of compliance with medical software certification directives. This was followed by the design and development of several software services aimed at allowing the communication of the environments applications and other components of the control system, such as remote file access, relational data access, and OPC-UA. In addition, several libraries and tools have been developed to support the development of future control system applications, following the defined product line architecture. Lastly, a pilot application was created using the tools developed during this work, as well as the preliminary results of a cross-environment integration project. The approach followed in this work is later evaluated by comparing the developed tools to their legacy counterparts, as well as estimating the impact of future applications following the defined product line architecture.Hadrontherapy is the treatment of cancer with charged ion beams. As the charged ion beams used in hadrontherapy are required to be accelerated to very large energies, the particle accelerators used in this treatment are complex and composed of several sub-systems. As a result, control systems are employed for the supervision and control of these accelerators. Currently, The Italian National Hadrontherapy Facility (CNAO) has the objective of modernizing one of the software environments of its control system. Such a project would allow for the integration of new types of devices into the control system, such as mobile devices, as well as introducing newer technologies into the environment. In order to achieve this, this work began with the requirement analysis and definition of a product line architecture for applications of the upgraded control system environment. The product line architecture focuses on reliability, maintainability, and ease of compliance with medical software certification directives. This was followed by the design and development of several software services aimed at allowing the communication of the environments applications and other components of the control system, such as remote file access, relational data access, and OPC-UA. In addition, several libraries and tools have been developed to support the development of future control system applications, following the defined product line architecture. Lastly, a pilot application was created using the tools developed during this work, as well as the preliminary results of a cross-environment integration project. The approach followed in this work is later evaluated by comparing the developed tools to their legacy counterparts, as well as estimating the impact of future applications following the defined product line architecture

A language and toolkit for the specification, execution and monitoring of dependable distributed applications

PhD ThesisThis thesis addresses the problem of specifying the composition of distributed applications out of existing applications, possibly legacy ones. With the automation of business processes on the increase, more and more applications of this kind are being constructed. The resulting applications can be quite complex, usually long-lived and are executed in a heterogeneous environment. In a distributed environment, long-lived activities need support for fault tolerance and dynamic reconfiguration. Indeed, it is likely that the environment where they are run will change (nodes may fail, services may be moved elsewhere or withdrawn) during their execution and the specification will have to be modified. There is also a need for modularity, scalability and openness. However, most of the existing systems only consider part of these requirements. A new area of research, called workflow management has been trying to address these issues. This work first looks at what needs to be addressed to support the specification and execution of these new applications in a heterogeneous, distributed environment. A co- ordination language (scripting language) is developed that fulfils the requirements of specifying the composition and inter-dependencies of distributed applications with the properties of dynamic reconfiguration, fault tolerance, modularity, scalability and openness. The architecture of the overall workflow system and its implementation are then presented. The system has been implemented as a set of CORBA services and the execution environment is built using a transactional workflow management system. Next, the thesis describes the design of a toolkit to specify, execute and monitor distributed applications. The design of the co-ordination language and the toolkit represents the main contribution of the thesis.UK Engineering and Physical Sciences Research Council, CaberNet, Northern Telecom (Nortel)

Dependability analysis of web services

Web Services form the basis of the web based eCommerce eScience applications so it is vital that robust services are developed. Traditional validation and verification techniques are centred around the concept of removing all faults to guarantee correct operation whereas Dependability gives an assessment of how dependably a system can deliver the required functionality by assessing attributes, and by eliminating threats via means attempts to improve dependability. Fault injection is a well-proven dependability assessment method. Although much work has been done in the area of fault injection and distributed systems in general, there appears to have been little research carried out on applying this to middleware systems and Web Services in particular. There are additional problems associated with applying existing fault injection technologies to Web Services running in a virtual machine environment since most are either invasive or work at a machine level. The Fault Injection Technology (FIT) method has been devised to address these problems for middleware systems. The Web Service-Fault Injection Technology (WS-FIT) implementation applies the FIT method, based on network level fault injection, to Web Services to create a non-invasive dependability assessment method. It allows targeted perturbation of Web Service RFC parameters as well as more traditional network level fault injection operations. The WS-FIT tool includes taxonomies that define a system under test, fault models to apply and failure modes to be detected, and uses these taxonomies to generate fault injection campaigns. WS-FIT has been applied to a number of case studies and has successfully demonstrated its effectiveness. It has also been successfully applied to a third-party system to evaluate dependability means. It performed this dependability assessment as well as allowing debugging of the means to be undertaken uncovering unknown faults

Initial CONNECT Architecture

Interoperability remains a fundamental challenge when connecting heterogeneous systems which encounter and spontaneously communicate with one another in pervasive computing environments. This challenge is exasperated by the highly heterogeneous technologies employed by each of the interacting parties, i.e., in terms of hardware, operating system, middleware protocols, and application protocols. The key aim of the CONNECT project is to drop this heterogeneity barrier and achieve universal interoperability. Here we report on the development of the overall CONNECT architecture that will underpin this solution; in this respect, we present the following contributions: i) an elicitation of interoperability requirements from a set of pervasive computing scenarios, ii) a survey of existing solutions to interoperability, iii) an initial view of the CONNECT architecture, and iv) a series of experiments to provide initial validation of the architecture

Distributed urban traffic applications based on CORBA event services

Intelligent transportation systems (ITS) in urban environments are based today on modern embedded systems with enhanced digital connectivity and higher processing capabilities, supporting distributed applications working in a cooperative manner. This paper provides an overview about modern cooperative ITS equipments and presents a distributed application to be used in an urban data network. As a case example, an application based on an embedded CORBA-compliant middleware layer and several computer vision equipments is presented. Results prove the feasibility of distributed applications for building intelligent urban environments

Combining Mobile Agents and Process-based Coordination to Achieve Software Adaptation

We have developed a model and a platform for end-to-end run-time monitoring, behavior and performance analysis, and consequent dynamic adaptation of distributed applications. This paper concentrates on how we coordinate and actuate the potentially multi-part adaptation, operating externally to the target systems, that is, without requiring any a priori built-in adaptation facilities on the part of said target systems. The actual changes are performed on the fly onto the target by communities of mobile software agents, coordinated by a decentralized process engine. These changes can be coarse-grained, such as replacing entire components or rearranging the connections among components, or fine-grained, such as changing the operational parameters, internal state and functioning logic of individual components. We discuss our successful experience using our approach in dynamic adaptation of a large-scale commercial application, which requires both coarse and fine grained modifications