Using policy to control data synchronisation in middleware for an ad-hoc mobile network

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Engineering Complex Computational Ecosystems

Self-organising pervasive ecosystems of devices are set to become a major vehicle for delivering infrastructure and end-user services. The inherent complexity of such systems poses new challenges to those who want to dominate it by applying the principles of engineering. The recent growth in number and distribution of devices with decent computational and communicational abilities, that suddenly accelerated with the massive diffusion of smartphones and tablets, is delivering a world with a much higher density of devices in space. Also, communication technologies seem to be focussing on short-range device-to-device (P2P) interactions, with technologies such as Bluetooth and Near-Field Communication gaining greater adoption. Locality and situatedness become key to providing the best possible experience to users, and the classic model of a centralised, enormously powerful server gathering and processing data becomes less and less efficient with device density. Accomplishing complex global tasks without a centralised controller responsible of aggregating data, however, is a challenging task. In particular, there is a local-to-global issue that makes the application of engineering principles challenging at least: designing device-local programs that, through interaction, guarantee a certain global service level. In this thesis, we first analyse the state of the art in coordination systems, then motivate the work by describing the main issues of pre-existing tools and practices and identifying the improvements that would benefit the design of such complex software ecosystems. The contribution can be divided in three main branches. First, we introduce a novel simulation toolchain for pervasive ecosystems, designed for allowing good expressiveness still retaining high performance. Second, we leverage existing coordination models and patterns in order to create new spatial structures. Third, we introduce a novel language, based on the existing ``Field Calculus'' and integrated with the aforementioned toolchain, designed to be usable for practical aggregate programming

A Comprehensive Framework for Testing Database-Centric Software Applications

The database is a critical component of many modern software applications. Recent reports indicate that the vast majority of database use occurs from within an application program. Indeed, database-centric applications have been implemented to create digital libraries, scientific data repositories, and electronic commerce applications. However, a database-centric application is very different from a traditional software system because it interacts with a database that has a complex state and structure. This dissertation formulates a comprehensive framework to address the challenges that are associated with the efficient and effective testing of database-centric applications. The database-aware approach to testing includes: (i) a fault model, (ii) several unified representations of a program's database interactions, (iii) a family of test adequacycriteria, (iv) a test coverage monitoring component, and (v) tools for reducing and re-ordering a test suite during regression testing.This dissertation analyzes the worst-case time complexity of every important testing algorithm. This analysis is complemented by experiments that measure the efficiency and effectiveness of thedatabase-aware testing techniques. Each tool is evaluated by using it to test six database-centric applications. The experiments show thatthe database-aware representations can be constructed with moderate time and space overhead. The adequacy criteria call for test suitesto cover 20% more requirements than traditional criteria and this ensures the accurate assessment of test suite quality. It is possibleto enumerate data flow-based test requirements in less than one minute and coverage tree path requirements are normally identified in no morethan ten seconds. The experimental results also indicate that the coverage monitor can insert instrumentation probes into all six of theapplications in fewer than ten seconds. Although instrumentation may moderately increase the static space overhead of an application, the coverage monitoring techniques only increase testing time by 55% on average. A coverage tree often can be stored in less than five seconds even though the coverage report may consume up to twenty-fivemegabytes of storage. The regression tester usually reduces or prioritizes a test suite in under five seconds. The experiments also demonstrate that the modified test suite is frequently more streamlined than the initial tests