A programming system for process coordination in virtual organisations

PhD thesisDistributed business applications are increasingly being constructed by composing them from services provided by various online businesses. Typically, this leads to trading partners coming together to form virtual organizations (VOs). Each member of a VO maintains their autonomy, except with respect to their agreed goals. The structure of the Virtual Organisation may contain one dominant organisation who dictates the method of achieving the goals or the members may be considered peers of equal importance. The goals of VOs can be defined by the shared global business processes they contain. To be able to execute these business processes, VOs require a flexible enactment model as there may be no single ‘owner’ of the business process and therefore no natural place to enact the business processes. One solution is centralised enactment using a trusted third party, but in some cases this may not be acceptable (for instance because of security reasons). This thesis will present a programming system that allows centralised as well as distributed enactment where each organisation enacts part of the business process. To achieve distributed enactment we must address the problem of specifying the business process in a manner that is amenable to distribution. The first contribution of this thesis is the presentation of the Task Model, a set of languages and notations for describing workflows that can be enacted in a centralised or decentralised manner. The business processes that we specify will coordinate the services that each organisation owns. The second contribution of this thesis is the presentation of a method of describing the observable behaviour of these services. The language we present, SSDL, provides a flexible and extensible way of describing the messaging behaviour of Web Services. We present a method for checking that a set of services described in SSDL are compatible with each other and also that a workflow interacts with a service in the desired manner. The final contribution of this thesis is the presentation of an abstract architecture and prototype implementation of a decentralised workflow engine. The prototype is able to enact workflows described in the Task Model notation in either a centralised or decentralised scenario

ATOMAS : a transaction-oriented open multi agent system; final report

The electronic marketplace of the future will consist of a large number of services located on an open, distributed and heterogeneous platform, which will be used by an even larger number of clients. Mobile Agent Systems are considered to be a precondition for the evolution of such an electronic market. They can provide a flexible infrastructure for this market, i.e. for the installation of new services by service agents as well as for the utilization of these services by client agents. Mobile Agent Systems basically consist of a number of locations and agents. Locations are (logical) abstractions for (physical) hosts in a computer network. The network of locations serves as a unique and homogeneous platform, while the underlying network of hosts may be heterogeneous and widely distributed. Locations therefore have to guarantee independence from the underlying hard- and software. To make the Mobile Agent System an open platform, the system furthermore has to guarantee security of hosts against malicious attacks

An Investigation Into the Mechanisms That Allow CORBA to Preserve Strong Typing

The Common Object Request Broker Architecture (CORBA) is a middleware specification. It aims at transparently extending programming languages to enable access to objects that are situated in different address spaces. Extending strongly typed languages raises the question whether the extension happens in a type-safe way. Claims are commonly made in the popular literature that this is indeed the case. However, this is not immediately clear from the specification. This thesis is an investigation into the different mechanisms that CORBA specifies to support remote operation invocations and a discussion of whether these mechanisms preserve type-safety for cross-boundary operation invocations. Successively, the object model, the type system, the architecture and the development process are reviewed. This is followed by a detailed investigation into the communications protocol used by CORBA, the server-side request dispatching mechanism and client-side operation invocation mechanisms. Conclusions drawn from these investigations are used to discuss type equivalence and the issues around interface evolution

The development of a discovery and control environment for networked audio devices based on a study of current audio control protocols

This dissertation develops a standard device model for networked audio devices and introduces a novel discovery and control environment that uses the developed device model. The proposed standard device model is derived from a study of current audio control protocols. Both the functional capabilities and design principles of audio control protocols are investigated with an emphasis on Open Sound Control, SNMP and IEC-62379, AES64, CopperLan and UPnP. An abstract model of networked audio devices is developed, and the model is implemented in each of the previously mentioned control protocols. This model is also used within a novel discovery and control environment designed around a distributed associative memory termed an object space. This environment challenges the accepted notions of the functionality provided by a control protocol. The study concludes by comparing the salient features of the different control protocols encountered in this study. Different approaches to control protocol design are considered, and several design heuristics for control protocols are proposed

A generic framework for process execution and secure multi-party transaction authorization

Process execution engines are not only an integral part of workflow and business process management systems but are increasingly used to build process-driven applications. In other words, they are potentially used in all kinds of software across all application domains. However, contemporary process engines and workflow systems are unsuitable for use in such diverse application scenarios for several reasons. The main shortcomings can be observed in the areas of interoperability, versatility, and programmability. Therefore, this thesis makes a step away from domain specific, monolithic workflow engines towards generic and versatile process runtime frameworks, which enable integration of process technology into all kinds of software. To achieve this, the idea and corresponding architecture of a generic and embeddable process virtual machine (ePVM), which supports defining process flows along the theoretical foundation of communicating extended finite state machines, are presented. The architecture focuses on the core process functionality such as control flow and state management, monitoring, persistence, and communication, while using JavaScript as a process definition language. This approach leads to a very generic yet easily programmable process framework. A fully functional prototype implementation of the proposed framework is provided along with multiple example applications. Despite the fact that business processes are increasingly automated and controlled by information systems, humans are still involved, directly or indirectly, in many of them. Thus, for process flows involving sensitive transactions, a highly secure authorization scheme supporting asynchronous multi-party transaction authorization must be available within process management systems. Therefore, along with the ePVM framework, this thesis presents a novel approach for secure remote multi-party transaction authentication - the zone trusted information channel (ZTIC). The ZTIC approach uniquely combines multiple desirable properties such as the highest level of security, ease-of-use, mobility, remote administration, and smooth integration with existing infrastructures into one device and method. Extensively evaluating both, the ePVM framework and the ZTIC, this thesis shows that ePVM in combination with the ZTIC approach represents a unique and very powerful framework for building workflow systems and process-driven applications including support for secure multi-party transaction authorization

An automatic song annotation system

Projecte final de carrera fet en col.laboració amb CCMAThe amount of multimedia content in the audiovisual sector, as well as on the Internet, is increasing a lot, and Music is one of the most outstanding forms of multimedia content requested by users. Every year, new songs, artists and genres appear in the market. Managing this musical content is, thus, becoming a very complex task. The present document presents the design and implementation of a system, that aims to solve the problem related to multimedia content management

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

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

Control-plane consistency in software-defined networking: distributed controller synchronization using the ISIS² toolkit

Software-defined Networking (SDN) is a recent approach in computer networks to ease the network administration by separating the control-plane and the data-plane. The data-plane only forwards packets according to certain rules specified by the control-plane. The control-plane, implemented by a software called controller, determines the forwarding rules based on a global view of the network. In order to increase fault tolerance and to eliminate a possible performance bottleneck, the controller can be distributed. The synchronization of the data that holds the global view is conventionally realized using distributed key-value stores offering a fixed consistency semantic, not respecting the heterogeneous consistency requirements of the data items in controller state. The virtual synchrony model, an alternative approach to the commonly used state machine replication method, offers a more flexible solution that can result in higher performance when certain assumptions on the data kept in controller state can be made. In this thesis a distributed controller based on OpenDaylight, a state-of-the-art SDN controller and the ISIS² library, that implements the virtual synchrony model, is proposed. The modular architecture of the proposed controller and the usage of a platform independent data model allows to extend or replace parts of the system. The implementation of the distributed controller is described and the macro and micro performance is evaluated with benchmarks.Software-defined Networking (SDN) ist ein aktueller Ansatz zu Computernetzwerken, der die Netzwerkadministration vereinfacht, in dem die Kontrollschicht von der Weiterleitungsschicht getrennt wird. Die Weiterleitungsschicht ist nur für das Weiterleiten von Paketen nach Regeln zuständig, die von der Kontrollschicht festgelegt werden. Die Kontrollschicht, die von einer Controller genannten Software implementiert wird, legt die Weiterleitungsregeln, basierend auf einer globalen Sicht auf das Netzwerk, fest. Um die Ausfallsicherheit zu erhöhen und um einen möglichen Leitungsengpass zu eliminieren kann der Controller verteilt werden. Die Synchronisation zwischen den Controllern wird herkömmlicherweise mithilfe von verteilten Key-Value Stores realisiert, die nur eine feste Konsistenzeigenschaft anbieten, was die heterogenen Konsistenzansprüche der Daten im Controllerzustand nicht berücksichtigt. Das Virtual Synchrony Modell, ein alternativer Ansatz zu der üblichen State-Machine Replication Methode, bietet eine flexiblere Lösung die zu höherer Leistung führen kann, wenn bestimmte Annahmen über die Daten im Controllerzustand gemacht werden können. Diese Arbeit stellt einen verteilten Controller basierend auf OpenDaylight, einem aktuellen SDN Controller und ISIS², einer Bibliothek die das Virtual Synchrony Modell umsetzt, vor. Die modulare Architektur des vorgestellten Controllers und die Verwendung eines plattformunabhänigen Datenmodells erlauben es, das System zu erweitern oder Komponenten zu ersetzen. Die Implementierung des verteilten Controllers wird beschrieben und die Komponenten und Gesamtleistung wird durch Benchmark-Tests ausgewertet