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Middleware wordt traditioneel gebruikt om de ontwikkeling van gedistribueerde applicaties te vergemakkelijken. Maar de omvang en complexiteit van gedistribueerde applicaties en het onderliggende middleware platform zijn aanzienlijk gegroeid. De groeiende populariteit van nieuwe paradigma’s zoals dienstgeoriënteerde ontwikkeling en het modelleren van bedrijfsprocessen vereisen de mogelijkheid om herbruikbare diensten te configureren om te voldoen aan applicatiespecifieke vereisten. De traditionele middleware architectuur dient uitgebreid te worden met een extra laag die de eenvoudige configuratie van diensten toelaat. Dit onderzoek stelt een policy-gebaseerde aanpak voor om de configuratie van diensten op een hoog niveau mogelijk te maken. Onze "policy-gedreven middleware" breidt de standaard middleware architectuur uit met een extra laag die complexiteit verbergt waar mogelijk en die het ontwikkelen van applicaties vereenvoudigt door ondersteuning te bieden voor het specificeren, valideren en afdwingen van policies. Policies zijn declaratieve statements op een hoger niveau die bepaalde keuzes in het systeem sturen. Onze belangrijkste contributies hebben zich toegespitst op drie dimensies die essentieel zijn in de zoektocht naar praktische oplossingen: (1) een expressieve policy taal die in verschillende contexten en toepassingsdomeinen kan gebruikt worden; (2) de integratie van het afdwingen van policies in de middleware, gebruik makend van verschillende strategieën en technieken; en (3) ondersteuning voor het redeneren over policies op basis van een hybride redeneersysteem. Een laatste contributie om de ontwikkeling van gedistribueerde applicaties te vergemakkelijken is uitgevoerd in de context van bedrijfsprocessen. Huidige talen voor het beschrijven van uitvoerbare bedrijfsprocessen bieden weinig ondersteuning voor het modulariseren van verschillende belangen, waardoor ze moeilijk(er) te verstaan, te onderhouden en te herbruiken zijn. Aspect-georiënteerde softwareontwikkeling is een gekende techniek om de modularisatie van een applicatie te verbeteren door verschillende belangen in aparte modules te specificeren. De Padus taal is een aspect-georiënteerde extensie voor WS-BPEL, een populaire workflow taal voor beschrijven van (web) service composities. Padus is specifiek ontwikkeld om bijkomende belangen van de hoofdfunctionaliteit van een bedrijfsproces te scheiden op basis van aspecten. Deze aspecten kunnen daarna gecombineerd worden met verschillende bedrijfsprocessen, gebruik makend van de statische Padus wever. Deze technologie kan ook gebruikt worden in policy-gedreven middleware om de integratie tussen policies en bedrijfsprocessen te vergemakkelijken. De contributies werden gevalideerd in realistische applicaties uit twee toepassingsdomeinen, namelijk de telecommunicatie en de gezondheidszorg. Middleware has traditionally been used to simplify the development of large-scale, distributed applications. However, the scope and complexity of distributed applications and of the underlying middleware platform has increased considerably. Furthermore, the growing popularity of new paradigms like service-oriented computing and business process management requires the customization of reusable services to match application-specific requirements. There is a need to extend the traditional middleware architecture with an extra layer that (further) hides complexity whenever possible and enables simplified application creation, customization and deployment. This research presents a policy-based approach for supporting the high-level configuration of services, integrated into the middleware platform. Policies are high-level, declarative statements governing choices in the behavior of a system. Our "policy-driven middleware" extends the traditional middleware architecture with an extra layer that hides complexity when possible and enables simplified application development and maintenance by offering the means to express, validate and enforce policies. Our main contributions are related to three dimensions that are essential in the search for practical solutions: (1) an expressive policy language that can be used in different areas and application domains; (2) the integration of policy enforcement in the middleware using different strategies and techniques; and (3) the support for policy reasoning capabilities using a hybrid reasoner. A final contribution to simplify the development of distributed applications is related to the area of business process management. Current business process languages suffer from poor support for separation of concerns, making them hard to understand, update, manage and reuse. Aspect-oriented software development is a well-known technique to improve modularization by allowing crosscutting concerns to be specified in separate modules called aspects. Padus is an aspect-oriented extension to WS-BPEL – a popular workflow language in the context of (web) service composition – that supports the separation of additional concerns from the main process functionality using aspects. These aspects can be applied to specific business processes using the static Padus weaver. This technology can also be used in our policy-driven middleware as a powerful candidate for integrating policies with business processes. Contributions have been validated in real-world applications in the domain of a telecom service delivery platform and a cross-enterprise healthcare informatics platform.

Academic collection --- 681.3*H <043> --- 681.3*C24 <043> --- Information systems--Dissertaties --- Distributed systems: distributed databases; distributed applications; networkoperating systems--Dissertaties --- Theses --- 681.3*C24 <043> Distributed systems: distributed databases; distributed applications; networkoperating systems--Dissertaties --- 681.3*H <043> Information systems--Dissertaties

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The behaviour of systems occurring in real life is often modelled by partial differential equations. This book investigates how a user or observer can influence the behaviour of such systems mathematically and computationally. A thorough mathematical analysis of controllability problems is combined with a detailed investigation of methods used to solve them numerically, these methods being validated by the results of numerical experiments. In Part I of the book the authors discuss the mathematics and numerics relating to the controllability of systems modelled by linear and non-linear diffusion equations; Part II is dedicated to the controllability of vibrating systems, typical ones being those modelled by linear wave equations; finally, Part III covers flow control for systems governed by the Navier-Stokes equations modelling incompressible viscous flow. The book is accessible to graduate students in applied and computational mathematics, engineering and physics; it will also be of use to more advanced practitioners.

Control theory --- Distributed parameter systems --- Differential equations, Partial --- Numerical solutions --- Control theory. --- Distributed parameter systems. --- Systems, Distributed parameter --- Engineering systems --- System analysis --- Numerical analysis --- Dynamics --- Machine theory --- Numerical solutions. --- Differential equations, Partial - Numerical solutions

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Computer security --- Electronic data processing --- Distributed processing --- Computer security. --- Distributed processing. --- 681.3*D46 --- 681.3*D47 --- 681.3*E3 --- 681.3*K65 --- Distributed computer systems in electronic data processing --- Distributed computing --- Distributed processing in electronic data processing --- Computer networks --- Computer privacy --- Computer system security --- Computer systems --- Computers --- Electronic digital computers --- Security of computer systems --- Data protection --- Security systems --- Hacking --- Security and protection: access controls; authentication; cryptographic controls; information flow controls; security kernels; verification (Operating systems) --- Organization and design: batch processing systems; distributed systems; hierarchical design; interactive systems; real-time systems (Operating systems) --- Data encryption: data encryption standard; DES; public key cryptosystems --- Security and protection: authentication; insurance; invasive software (e.g. viruses, worms, Trojan horses); physical security; unauthorized access (e.g. hacking, phreaking) --- Security measures --- 681.3*E3 Data encryption: data encryption standard; DES; public key cryptosystems --- 681.3*D47 Organization and design: batch processing systems; distributed systems; hierarchical design; interactive systems; real-time systems (Operating systems) --- 681.3*D46 Security and protection: access controls; authentication; cryptographic controls; information flow controls; security kernels; verification (Operating systems) --- Security engineering --- Information Technology --- General and Others --- Cyber security --- Cybersecurity --- Protection of computer systems --- Protection --- Electronic data processing - Distributed processing

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Computer networks --- Computer security --- Digital communications --- 6813*C20 --- 681.3*D46 --- 681.3*D47 --- 681.3*E3 --- Communications, Digital --- Digital transmission --- Pulse communication --- Digital electronics --- Pulse techniques (Electronics) --- Telecommunication --- Digital media --- Signal processing --- Computer privacy --- Computer system security --- Computer systems --- Computers --- Cyber security --- Cybersecurity --- Electronic digital computers --- Protection of computer systems --- Security of computer systems --- Data protection --- Security systems --- Hacking --- Computer network security --- Network security, Computer --- Security of computer networks --- 681.3*E3 Data encryption: data encryption standard; DES; public key cryptosystems --- Data encryption: data encryption standard; DES; public key cryptosystems --- 681.3*D47 Organization and design: batch processing systems; distributed systems; hierarchical design; interactive systems; real-time systems (Operating systems) --- Organization and design: batch processing systems; distributed systems; hierarchical design; interactive systems; real-time systems (Operating systems) --- 681.3*D46 Security and protection: access controls; authentication; cryptographic controls; information flow controls; security kernels; verification (Operating systems) --- Security and protection: access controls; authentication; cryptographic controls; information flow controls; security kernels; verification (Operating systems) --- Security measures --- Computer-communication networks: general: data communications, open systems interconnection reference model (OSI), security and protection (e.g., firewalls) --- Digital techniques --- Protection --- Computer networks - Security measures --- Digital communications - Security measures