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

An agent-based service-oriented approach to evolving legacy software systems into a pervasive computing environment.

This thesis focuses on an Agent-Based Service-Oriented approach to evolving legacy system into a Pervasive Computing environment. The methodology consists of multiple phases: using reverse engineering techniques to comprehend and decompose legacy systems, employing XML and Web Services to transform and represent a legacy system as pervasive services, and integrating these pervasive services into pervasive computing environments with agent based integration technology. A legacy intelligent building system is used as a case study for experiments with the approach, which demonstrates that the proposed approach has the ability to evolve legacy systems into pervasive service environments seamlessly. Conclusion is drawn based on analysis and further research directions are also discussed

Towards a model for teaching distributed computing in a distance-based educational environment

Several technologies and languages exist for the development and implementation of distributed systems. Furthermore, several models for teaching computer programming and teaching programming in a distance-based educational environment exist. Limited literature, however, is available on models for teaching distributed computing in a distance-based educational environment. The focus of this study is to examine how distributed computing should be taught in a distance-based educational environment so as to ensure effective and quality learning for students. The required effectiveness and quality should be comparable to those for students exposed to laboratories, as commonly found in residential universities. This leads to an investigation of the factors that contribute to the success of teaching distributed computing and how these factors can be integrated into a distance-based teaching model. The study consisted of a literature study, followed by a comparative study of available tools to aid in the learning and teaching of distributed computing in a distance-based educational environment. A model to accomplish this teaching and learning is then proposed and implemented. The findings of the study highlight the requirements and challenges that a student of distributed computing in a distance-based educational environment faces and emphasises how the proposed model can address these challenges. This study employed qualitative research, as opposed to quantitative research, as qualitative research methods are designed to help researchers to understand people and the social and cultural contexts within which they live. The research methods employed are design research, since an artefact is created, and a case study, since “how” and “why” questions need to be answered. Data collection was done through a survey. Each method was evaluated via its own well-established evaluation methods, since evaluation is a crucial component of the research process.ComputingM. Sc. (Computer Science

UBIDEV: a homogeneous service framework for pervasive computing environments

This dissertation studies the heterogeneity problem of pervasive computing system from the viewpoint of an infrastructure aiming to provide a service-oriented application model. From Distributed System passing through mobile computing, pervasive computing is presented as a step forward in ubiquitous availability of services and proliferation of interacting autonomous entities. To better understand the problems related to the heterogeneous and dynamic nature of pervasive computing environments, we need to analyze the structure of a pervasive computing system from its physical and service dimension. The physical dimension describes the physical environment together wit the technology infrastructure that characterizes the interactions and the relations within the environment; the service dimension represents the services (being them software or not) the environment is able to provide [Nor99]. To better separate the constrains and the functionalities of a pervasive computing system, this dissertation classifies it in terms of resources, context, classification, services, coordination and application. UBIDEV, as the key result of this dissertation, introduces a unified model helping the design and the implementation of applications for heterogeneous and dynamic environments. This model is composed of the following concepts: • Resource: all elements of the environment that are manipulated by the application, they are the atomic abstraction unit of the model. • Context: all information coming from the environment that is used by the application to adapts its behavior. Context contains resources and services and defines their role in the application. • Classification: the environment is classified according to the application ontology in order to ground the generic conceptual model of the application to the specific environment. It defines the basic semantic level of interoperability. • Service: the functionalities supported by the system; each service manipulates one or more resources. Applications are defined as a coordination and adaptation of services. • Coordination: all aspects related to service composition and execution as well as the use of the contextual information are captured by the coordination concept. • Application Ontology: represents the viewpoint of the application on the specific context; it defines the high level semantic of resources, services and context. Applying the design paradigm proposed by UBIDEV, allows to describe applications according to a Service Oriented Architecture[Bie02], and to focus on application functionalities rather than their relations with the physical devices. Keywords: pervasive computing, homogenous environment, service-oriented, heterogeneity problem, coordination model, context model, resource management, service management, application interfaces, ontology, semantic services, interaction logic, description logic.Questa dissertazione studia il problema della eterogeneit`a nei sistemi pervasivi proponendo una infrastruttura basata su un modello orientato ai servizi. I sistemi pervasivi sono presentati come un’evoluzione naturale dei sistemi distribuiti, passando attraverso mobile computing, grazie ad una disponibilit`a ubiqua di servizi (sempre, ovunque ed in qualunque modo) e ad loro e con l’ambiente stesso. Al fine di meglio comprendere i problemi legati allintrinseca eterogeneit`a dei sistemi pervasivi, dobbiamo prima descrivere la struttura fondamentale di questi sistemi classificandoli attraverso la loro dimensione fisica e quella dei loro servizi. La dimensione fisica descrive l’ambiente fisico e tutti i dispositivi che fanno parte del contesto della applicazione. La dimensione dei servizi descrive le funzionalit`a (siano esse software o no) che l’ambiente `e in grado di fornire [Nor99]. I sistemi pervasivi vengono cos`ı classificati attraverso una metrica pi `u formale del tipo risorse, contesto, servizi, coordinazione ed applicazione. UBIDEV, come risultato di questa dissertazione, introduce un modello uniforme per la descrizione e lo sviluppo di applicazioni in ambienti dinamici ed eterogenei. Il modello `e composto dai seguenti concetti di base: • Risorse: gli elementi dell’ambiente fisico che fanno parte del modello dellapplicazione. Questi rappresentano l’unit`a di astrazione atomica di tutto il modello UBIDEV. • Contesto: le informazioni sullo stato dell’ambiente che il sistema utilizza per adattare il comportamento dell’applicazione. Il contesto include informazioni legate alle risorse, ai servizi ed alle relazioni che li legano. • Classificazione: l’ambiente viene classificato sulla base di una ontologia che rappresenta il punto di accordo a cui tutti i moduli di sistema fanno riferimento. Questa classificazione rappresenta il modello concettuale dell’applicazione che si riflette sull’intero ambiente. Si definisce cos`ı la semantica di base per tutto il sistema. • Servizi: le funzionalit`a che il sistema `e in grado di fornire; ogni servizio `e descritto in termini di trasformazione di una o pi `u risorse. Le applicazioni sono cos`ı definite in termini di cooperazione tra servizi autonomi. • Coordinazione: tutti gli aspetti legati alla composizione ed alla esecuzione di servizi cos`ı come l’elaborazione dell’informazione contestuale. • Ontologia dell’Applicazione: rappresenta il punto di vista dell’applicazione; definisce la semantica delle risorse, dei servizi e dell’informazione contestuale. Applicando il paradigma proposto da UBIDEV, si possono descrivere applicazioni in accordo con un modello Service-oriented [Bie02] ed, al tempo stesso, ridurre l’applicazione stessa alle sue funzionalit`a di alto livello senza intervenire troppo su come queste funzionalit` a devono essere realizzate dalle singole componenti fisiche

How To Touch a Running System

The increasing importance of distributed and decentralized software architectures entails more and more attention for adaptive software. Obtaining adaptiveness, however, is a difficult task as the software design needs to foresee and cope with a variety of situations. Using reconfiguration of components facilitates this task, as the adaptivity is conducted on an architecture level instead of directly in the code. This results in a separation of concerns; the appropriate reconfiguration can be devised on a coarse level, while the implementation of the components can remain largely unaware of reconfiguration scenarios. We study reconfiguration in component frameworks based on formal theory. We first discuss programming with components, exemplified with the development of the cmc model checker. This highly efficient model checker is made of C++ components and serves as an example for component-based software development practice in general, and also provides insights into the principles of adaptivity. However, the component model focuses on high performance and is not geared towards using the structuring principle of components for controlled reconfiguration. We thus complement this highly optimized model by a message passing-based component model which takes reconfigurability to be its central principle. Supporting reconfiguration in a framework is about alleviating the programmer from caring about the peculiarities as much as possible. We utilize the formal description of the component model to provide an algorithm for reconfiguration that retains as much flexibility as possible, while avoiding most problems that arise due to concurrency. This algorithm is embedded in a general four-stage adaptivity model inspired by physical control loops. The reconfiguration is devised to work with stateful components, retaining their data and unprocessed messages. Reconfiguration plans, which are provided with a formal semantics, form the input of the reconfiguration algorithm. We show that the algorithm achieves perceived atomicity of the reconfiguration process for an important class of plans, i.e., the whole process of reconfiguration is perceived as one atomic step, while minimizing the use of blocking of components. We illustrate the applicability of our approach to reconfiguration by providing several examples like fault-tolerance and automated resource control

Event management for mobile users

This technical report presents the results of the project "Event Management for Mobile Users", a research cooperation between Universität Stuttgart and Microsoft. In Vienna, Microsoft chief executive Bill Gates recently expressed his vision of a seamless interaction of different computing devices, from PC to mobile phone, that proactively support the users wherever they go. Among other things, he said: "For example, if you want to be notified about something that's changing, that's important to you, software should know which device you have with you and should know what you're doing, know the context to understand if interrupting you with this new information is appropriate or not." (Bill Gates, January 28, 2004, [Los Angeles Times 2004]) This project may present one step towards realizing his vision. It is about event support for mobile users. Depending on their current context, they want to be informed about events that occur in the world around them - the physical as well as the virtual world of digital information systems. So, to optimally support its users, future generations of web services will need information about the real-world context of the user, especially their spatial context. This project was carried out in close cooperation with the Nexus project at Universität Stuttgart, whose goal is to support mobile context-aware applications based on a distributed spatial world model. Events of special interest in this context are spatial events, i.e. events that occur when a certain spatial constellation of objects is reached, e.g. when two people meet or when a customer enters a shopping mall. As the underlying world model is distributed, the events have to be observed on a distributed model. The number of potential spatial events is not restricted, e.g. the event that a user enters an area could be of interest for arbitrary areas. Also, as the spatial world model is distributed over many servers, a local observation is no longer sufficient. Therefore, the well-known publish-subscribe paradigm, in which the observation occurs implicitly within local observers, has to be extended. We propose an observation-notification paradigm, in which the observation of events has to be explicitly initiated by interested clients. The event service that conforms to the new paradigm consists of two components: an observation service, which observes events through a distributed model, and a notification service, which efficiently delivers event notifications. This paradigm applies to all scenarios in which the data needed for the observation of events is distributed over multiple sources. The user wants the specification of events to be as simple and easy as possible. He only wants to specify what event is to be observed, not how the observation of the event is realized. Therefore the distribution aspects should be transparent to the user. However, these aspects have a strong influence on the accuracy of the model and thereby directly affect the accuracy of event observation. We propose that the user specifies an event as a predicate, which becomes true when the event has occurred, plus a threshold probability. If the probability that the event has occurred is above the threshold probability, the event is considered to have occurred and an event notification is sent. The above sketched solution requires calculating the probability with which an event has occurred. We first show which parameters influence the accuracy of the data. We then present update protocols that guarantee a certain accuracy of data in the observer model, i.e. the model where the event is actually observed. Finally we show, how the occurrence probability can be calculated. Based on the identified parameters, the placement of the observation in the system can also be optimized with regard to the accuracy of the data. We have implemented the event service and integrated it into the Nexus platform. As the Nexus platform is intended as an open platform with possibly world-wide scale, scalability, efficiency and interoperability have been important requirements for the design of the components. To support interoperability, we have built on standard technologies like XML, HTTP and SOAP. The evaluation of the event service within the Nexus context shows the feasibility of the approach. We were able to show that the event service performs adequately in certain example scenarios. Experiments with a large-scale scenario are the next steps on our agenda

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

Context-Aware Software

With the advent of PDAs (Personal Digital Assistants), smart phones, and other forms of mobile and ubiquitous computers, our computing resources are increasingly moving off of our desktops and into our everyday lives. However, the software and user interfaces for these devices are generally very similar to that of their desktop counterparts, despite the radically different and dynamic environments that they face. We propose that to better assist their users, such devices should be able to sense, react to, and utilise, the user's current environment or context. That is, they should become context-aware. In this thesis we investigate context-awareness at three levels: user interfaces, applications, and supporting architectures/frameworks. To promote the use of context-awareness, and to aid its deployment in software, we have developed two supporting frameworks. The first is an application-oriented framework called stick-e notes. Based on an electronic version of the common Post-It Note, stick-e notes enable the attachment of any electronic resource (e.g. a text file, movie, Java program, etc.) to any type of context (e.g. location, temperature, time, etc.). The second framework we devised seeks to provide a more universal support for the capture, manipulation, and representation of context information. We call it the Context Information Service (CIS). It fills a similar role in context-aware software development as GUI libraries do in user interface development. Our applications research explored how context-awareness can be exploited in real environments with real users. In particular, we developed a suite of PDA-based context-aware tools for fieldworkers. These were used extensively by a group of ecologists in Africa to record observations of giraffe and rhinos in a remote Kenyan game reserve. These tools also provided the foundations for our HCI work, in which we developed the concept of the Minimal Attention User Interface (MAUI). The aim of the MAUI is to reduce the attention required by the user in operating a device by carefully selecting input/output modes that are harmonious to their tasks and environment. To evaluate our ideas and applications a field study was conducted in which over forty volunteers used our system for data collection activities over the course of a summer season at the Kenyan game reserve. The PDA-based tools were unanimously preferred to the paper-based alternatives, and the context-aware features were cited as particular reasons for preferring them. In summary, this thesis presents two frameworks to support context-aware software, a set of applications demonstrating how context-awareness can be utilised in the ''real world'', and a set of HCI guidelines and principles that help in creating user interfaces that fit to their context of use

Dynamic Rule-Based Reasoning in Smart Environments

Slimme huizen en andere soorten slimme omgevingen kunnen worden gedefinieerd door verschillende belangrijke karakteristieken. De belangrijkste hiervan is ongetwijfeld de mogelijkheid om omgevingsbewust te zijn, om de fysieke omgeving te ervaren en om de context van de huidige situatie te begrijpen. Slimme omgevingen zouden in staat moeten zijn om met deze informatie te kunnen redeneren en waardevolle kennis te kunnen afleiden. Daarnaast zullen ze de mogelijkheid moeten hebben om intelligent te reageren in reactie op veranderende situaties, volgens bepaalde doelstellingen. Slimme omgevingen zijn vaak ubiquitous, wat betekent dat hun capaciteiten voor waarnemen en handelen berusten op apparaten die zijn ingebed in de fysieke wereld. De meeste van de huidige commerciele slimme omgevingsproducten presenteren slechts gedeeltelijke oplossingen, zoals automatische verlichting of energiebewustzijn. Verschillende factoren vertragen de commercialisering van volledig slimme huizen, waaronder de noodzaak om de oplossing op iedere nieuwe locatie opnieuw zeer nauwkeurig af te stellen, de inspanningen rondom de integratie en co'ordinatie van verschillende componenten, handelingen om een consistent model over verschillende subsystemen van verschillende bronnen samen te stellen, enzovoorts. Samenvattend, de grote hoeveelheid aan inspanningen die benodigd zijn om de oplossing van een locatie naar een andere te verplaatsen hindert de mogelijkheden voor het stroomlijnen van de uitrol. Wat zijn de overeenkomsten in het ontwerp en het ontwikkelproces van een slimme omgeving? Wat is een effectieve aanpak om een redeneringsmotor voor slimme omgevingen te ontwerpen die aan alle belangrijke vereisten voldoet? Hoe kan het effect van sensorfouten voor wat betreft de besluitvorming worden geminimaliseerd? Hoe kan een slim systeem het bestaan van verschillende energieleveranciers gebruiken om de energiekosten in de tijd te minimaliseren? In dit proefschrift bespreken we en geven we antwoord op een aantal belangrijke onderzoeksvraagstukken voor huidige pervasieve systemen, slimme omgevingen in het bijzonder

A semantic approach for scalable and self-organized context-aware systems

Ph.DDOCTOR OF PHILOSOPH