Dissertation com feb 1999 (2 risultati)

Taschenbuch. Condizione: Neu. Neuware - Comprehensive global garbage detection (GGD) in object-oriented distributed systems, i.e., GGD intrinsically able to detect distributed cycles of garbage, has mostly been addressed via graph tracing algorithms. Graph tracing algorithms must account for every live object in the system before any resource can actually be reclaimed which compromises both their scalability and robustness in a distributed environment.Alternative non-comprehensive approaches trade-off comprehensiveness for scalability and robustness under the assumptions that distributed cycles of garbage are rare and that all comprehensive algorithms are necessarily unscalable. This thesis contends instead that distributed cycles of garbage are as likely to occur as local cycles and that a comprehensive alternative to graph tracing GGD is possible.From the GGD perspective, the combined effects of the application processes and local garbage collectors fulfill the role of a global mutator. A subset of events of this global mutator's computation, called log-keeping events, reflect either the creation, or the destruction, of inter-site paths in the global object graph. The causal history of a log-keeping event corresponds to the set of events responsible for the creation of all the paths ever created that are incident to an object. The path history of this event is defined as a subset of its causal history and contains only those events responsible for the creation of the extant paths to this object.This dissertation presents a novel approach to comprehensive GGD that entails computing dependency vectors which characterize the path history of log-keeping events that reflect the destruction of a path. These dependency vectors can be computed by propagating increasingly accurate approximations of these vectors along the paths of the global object graph. In effect, this algorithm reacts to events that may result in the creation of garbage and identifies garbage without requiring a complete scan of the whole object graph. In conjunction with a lazy log-keeping mechanism, it can therefore be shown to be both scalable and robust despite being comprehensive.…

Taschenbuch. Condizione: Neu. Neuware - How does the state system measure up to today's realitites when it comes to managing conflict To what extent are efforts to manage conflict successful, and for whom Prevailing structures designed to deal with conflict between collectives -- sovereign states supported by militaries, military industry, and the United Nations -- operate mainly on principles that are hundreds of years old. Conditions for conflict and its management have changed radically since this state system was constructed. There is a risk that institutional inertia produces growing disparity between real-world problems and the institutions that are supposed to manage them.Realism and legalism are found to form a double idological support for the state system. The study compares the state system's realist and legalist premises to different cases of post cold war intercollective conflict: the 1990-91 Gulf War, the 1990-95 break-up of Yugoslavia, and the 1992 Los Angeles riots. These cases present important challenges to the pravailing system's premises -- mismatches between idea and reality that are clearly connected to failures in conflict management. In addition, findings suggest that the state system not only fails to deal with important aspects of modern-day conflict, but that it increasingly produces problems that it cannot manage. This suggests that the prevailing state system is not in harmony with crucial conflict-related aspects of global impact, indicating a serious systemic problem.…