Intergiciel d'intergiciels adaptable à base de Services, Composants et Aspects

Cette habilitation à diriger des recherches présente mes travaux sur le génie logiciel des intergiciels, domaine à la croisée de l’informatique répartie et du génie logiciel. L’intergiciel est la couche logicielle permettant de s’abstraire de l’hétérogénéité des technologies de l’informatique distribuée et de répondre aux besoins d’interopérabilité, de portabilité, d’adaptation et de séparation des préoccupations des applications réparties. Mes travaux ont été guidés par deux questions de recherche ouvertes : 1) quel est le paradigme de programmation le plus approprié pour les applications réparties ? 2) quelle est l’organisation la plus appropriée pour l’intergiciel ?La première partie présente une synthèse de mes travaux et contributions. Premièrement, mes travaux ont porté sur la transition des objets vers les composants CORBA donnant lieu à deux contributions majeures : le langage de script CorbaScript standardisé auprès de l’OMG et la plate-forme OpenCCM pour le développement, le déploiement, l’exécution et l’administration d’applications réparties à base de composants CORBA. Deuxièmement, je me suis intéressé à la conception de canevas intergiciels hautement adaptables. Ces travaux basés sur les composants réflexifs Fractal ont donné lieu à un cadre de programmation par attributs sur lequel trois canevas flexibles pour la gestion du transactionnel, le déploiement de systèmes distribués hétérogènes et les composants Java temps-réels ont été bâtis. Enfin, mes travaux ont porté sur la proposition du modèle Services Composants Aspects (SCA) et l’intergiciel d’intergiciels FraSCAti.La deuxième partie opère un zoom sur le projet FraSCAti. La contribution scientifique de ce projet est de proposer un intergiciel réflexif pour l’informatique orientée service combinant deux idées originales : la notion d’intergiciel d’intergiciels et le modèle Services Composants Aspects réflexif. Partant du constat qu’il n’existe pas d’intergiciel universel capable de couvrir l’ensemble des besoins de toutes les applications distribuées, le projet FraSCAti propose un canevas intergiciel extensible pour l’intégration et la composition élégante des intergiciels et technologies SOA existants, c’est-à-dire un intergiciel d’intergiciels. Le modèle SCA réflexif est quant à lui le mariage fécond du standard OASIS Service Component Architecture (SCA), du modèle de composants Fractal et de la programmation orientée aspects (AOP). Dans ce modèle, tout est composant réflexif permettant ainsi d’adapter dynamiquement aussi bien les applications métiers, l’intergiciel, les liaisons de communication réseau que les aspects non fonctionnels. Cette contribution a été appliquée sur l’orchestration de services à large échelle, la construction de systèmes de systèmes et une plate-forme distribuée multi-nuages. La dernière partie dresse un bilan des contributions et présente mes perspectives de recherche centrées sur le génie logiciel pour l’informatique en nuage (cloud computing)

Adaptive Caching of Distributed Components

Die Zugriffslokalität referenzierter Daten ist eine wichtige Eigenschaft verteilter Anwendungen. Lokales Zwischenspeichern abgefragter entfernter Daten (Caching) wird vielfach bei der Entwicklung solcher Anwendungen eingesetzt, um diese Eigenschaft auszunutzen. Anschliessende Zugriffe auf diese Daten können so beschleunigt werden, indem sie aus dem lokalen Zwischenspeicher bedient werden. Gegenwärtige Middleware-Architekturen bieten dem Anwendungsprogrammierer jedoch kaum Unterstützung für diesen nicht-funktionalen Aspekt. Die vorliegende Arbeit versucht deshalb, Caching als separaten, konfigurierbaren Middleware-Dienst auszulagern. Durch die Einbindung in den Softwareentwicklungsprozess wird die frühzeitige Modellierung und spätere Wiederverwendung caching-spezifischer Metadaten gewährleistet. Zur Laufzeit kann sich das entwickelte System außerdem bezüglich der Cachebarkeit von Daten adaptiv an geändertes Nutzungsverhalten anpassen.Locality of reference is an important property of distributed applications. Caching is typically employed during the development of such applications to exploit this property by locally storing queried data: Subsequent accesses can be accelerated by serving their results immediately form the local store. Current middleware architectures however hardly support this non-functional aspect. The thesis at hand thus tries outsource caching as a separate, configurable middleware service. Integration into the software development lifecycle provides for early capturing, modeling, and later reuse of cachingrelated metadata. At runtime, the implemented system can adapt to caching access characteristics with respect to data cacheability properties, thus healing misconfigurations and optimizing itself to an appropriate configuration. Speculative prefetching of data probably queried in the immediate future complements the presented approach

An Object-Based Software Distribution Network

Steen, M.R. [Promotor]van Tanenbaum, A.S. [Promotor

Faculty Publications and Creative Works 1997

One of the ways we recognize our faculty at the University of New Mexico is through this annual publication which highlights our faculty\u27s scholarly and creative activities and achievements and serves as a compendium of UNM faculty efforts during the 1997 calendar year. Faculty Publications and Creative Works strives to illustrate the depth and breadth of research activities performed throughout our University\u27s laboratories, studios and classrooms. We believe that the communication of individual research is a significant method of sharing concepts and thoughts and ultimately inspiring the birth of new of ideas. In support of this, UNM faculty during 1997 produced over 2,770 works, including 2,398 scholarly papers and articles, 72 books, 63 book chapters, 82 reviews, 151 creative works and 4 patents. We are proud of the accomplishments of our faculty which are in part reflected in this book, which illustrates the diversity of intellectual pursuits in support of research and education at the University of New Mexico. Nasir Ahmed Interim Associate Provost for Research and Dean of Graduate Studie

Models of higher-order, type-safe, distributed computation over autonomous persistent object stores

A remote procedure call (RPC) mechanism permits the calling of procedures in another address space. RPC is a simple but highly effective mechanism for interprocess communication and enjoys nowadays a great popularity as a tool for building distributed applications. This popularity is partly a result of their overall simplicity but also partly a consequence of more than 20 years of research in transpaxent distribution that have failed to deliver systems that meet the expectations of real-world application programmers. During the same 20 years, persistent systems have proved their suitability for building complex database applications by seamlessly integrating features traditionally found in database management systems into the programming language itself. Some research. effort has been invested on distributed persistent systems, but the outcomes commonly suffer from the same problems found with transparent distribution. In this thesis I claim that a higher-order persistent RPC is useful for building distributed persistent applications. The proposed mechanism is: realistic in the sense that it uses current technology and tolerates partial failures; understandable by application programmers; and general to support the development of many classes of distributed persistent applications. In order to demonstrate the validity of these claims, I propose and have implemented three models for distributed higher-order computation over autonomous persistent stores. Each model has successively exposed new problems which have then been overcome by the next model. Together, the three models provide a general yet simple higher-order persistent RPC that is able to operate in realistic environments with partial failures. The real strength of this thesis is the demonstration of realism and simplicity. A higherorder persistent RPC was not only implemented but also used by programmers without experience of programming distributed applications. Furthermore, a distributed persistent application has been built using these models which would not have been feasible with a traditional (non-persistent) programming language

Security in Distributed, Grid, Mobile, and Pervasive Computing

This book addresses the increasing demand to guarantee privacy, integrity, and availability of resources in networks and distributed systems. It first reviews security issues and challenges in content distribution networks, describes key agreement protocols based on the Diffie-Hellman key exchange and key management protocols for complex distributed systems like the Internet, and discusses securing design patterns for distributed systems. The next section focuses on security in mobile computing and wireless networks. After a section on grid computing security, the book presents an overview of security solutions for pervasive healthcare systems and surveys wireless sensor network security

Concur: An Investigation of Lightweight Migration in Support of Centralized Synchronous Distributed Collaboration

Synchronous distributed collaborative systems support simultaneous observation of and interaction with shared objects by multiple, dispersed participants. Centralized architectures for such systems support simple user mental models and are comparatively easy to implement, but they suffer from high latency. Replicated architectures improve latency at the expense of more complex user mental models and implementations. Hybrid and dynamic architectures apply centralized and replicated sub-architectures in an attempt to get the best of both worlds, but in reality they further complicate implementations and user mental models. Concur is an architecture I developed to investigate lightweight migration as an alternative means to attain the best characteristics of centralized and replicated architectures. Previous dynamic architectures improved latency using the migration of heavyweight processes or (object-oriented) objects, which is costly in terms of migration time and runtime requirements. In Concur I have instead organized collaborative applications and supporting infrastructures around migrating entities which are not required to have full process or object semantics. These entities are classified by properties affecting migration, such as their size and their use of external references. In this way I achieved both the simpler user mental models and implementations of centralized systems and the superior latency characteristics of replicated systems. Concur accomplishes this through the fast migration of lightweight entities in a multi-centered centralized system, where a multi-centered system is defined as having single physical center and multiple, independently-migrating and entity-specific logical centers. This dissertation also identifies other significant advantages of the Concur architecture. Sub-object, easily-migratable entity classes minimize runtime requirements, facilitating widespread entity distribution. This in turn helps us to achieve the critical mass required for the success of any communication technology. The speed of lightweight entity migration also enables migrations to be triggered based on telegraphed user intentions (user actions that hint at imminent succeeding actions). I have demonstrated that telegraphed intentions are more accurate predictors of future interactions than the recent interaction histories considered in previous systems. Migrating entities based on these telegraphed intentions increases the probability that an entity will be located near a user when he begins to manipulate it

Privacy-preserving framework for context-aware mobile applications

In recent years, the pervasiveness of mobile devices, especially mobile phones and personal digital assistants (PDAs), has increased rapidly. At the same time, wireless communication networks have improved considerably and the usage of mobile devices to access the internet is, with decreasing costs, possible almost everywhere and at any time in industrialized countries. However, the usage of mobile technology and mobile applications to support business processes, trans- actions, and personal tasks is still low compared to their potential. The improved capabilities resulted in the introduction of many applications for mobile devices by network operators and software vendors. These services were meant to increase the average revenue per user (ARPU) on top of the voice call income. But many of these services have failed and none of them has led to an improved usage of mobile services today, besides e-mail. A new kind of application, the context-aware application, exploits the ubiquity of the mobile devices in order to fit the personal need or task the user is about to execute satisfactorily. Context-aware systems try to improve the communication with the user by adding information about the current context to the explicit user input and by adapting the output to the current setting of the user. While those applications are seen as important steps to a widespread usage, there are strong factors inhibiting their development and adoption. First of all, the lack of common frameworks handling context data and improv- ing software development increases the cost to build context-aware applications. Each application currently implements its own sensors and logic to handle its data. Furthermore, service providers need to offer tailored services for every con- text of the user. Since no single provider is able to be an expert for all kinds of applications and will not have the necessary number of developers, a common service which finds services of multiple providers for the current situation of the user is needed. All services need to utilize the context attributes which are locally determined by the user’s situation. Development costs are further boosted by the difficulty of developing applications for multiple devices with varying input/output (IO) capabilities like speech output, small and big screens, full qwerty-keyboards, touchscreens, or numeric keypads. From the user’s perspective, privacy also endangers the adoption of mobile services. Context information may include very private data and expose the user’s preferences and habits. While the user may trust a single, well-known, provider to secure the private data and to respect the user’s privacy concerns, the problem increases with more and more smaller service providers