Abstract not found

Abstract. Graphical illustrations of geographical distributions, ages and sizes of astronomy-related organizations are presented from comprehensive and up-to-date samples extracted from master files with validated data (StarGuides/StarWorlds). More detailed results for professional institutions, associations, planetariums, and public observatories are also presented and commented, as well as specific distributions for astronomyrelated publishers and commercial-software producers. The geographical distributions display a highly uneven general pattern which is very much the same as it was at the beginning of the XXth century, in spite of the fact that there are more astronomy-related organizations nowadays – another illustration of the well-known socio-economic effect of self-reinforcement. Other geographical peculiarities (local concentrations, national cultures and policies, electronic astronomy,...) are discussed in the paper, as well as the uneasy separation between amateur and professional astronomers in associations. A number of events had a clear impact on the rate of foundation of astronomy-related organizations, such as the two World Wars, the beginning of space exploration, the landing of man on the Moon, the end of the Cold War, spectacular astronomical episodes (such as bright comets) and so on. However, as detailed in the paper, not all of them affected in the same way Western Europe and North America, nor the various types of organizations. If the size of the vast majority of astronomy-related organizations is relatively small, there are however some differences between Western Europe and North America. 8 ANDRÉ HECK

This paper discusses fault-tolerant, scalable solutions to the problem of accurately and scalably calculating global aggregate functions in large process groups communicating over unreliable networks. These groups could represent sensors or processes communicating over a network that is either fixed (eg., the Internet) or dynamic (eg., multihop ad-hoc). Group members are prone to failures. The ability to evaluate global aggregate properties (eg., the average of sensor temperature readings) is important for higher-level coordination activities in such large groups. We first define the setting and problem, laying down metrics to evaluate different algorithms for the same. We discuss why the usual approaches to solve this problem are unviable and unscalable over an unreliable network prone to message delivery failures and crash failures. We then propose a technique to impose an abstract hierarchy on such large groups, describing how this hierarchy can be made to mirror the network topology. We discuss several alternatives to use this technique to solve the global aggregate function evaluation problem. Finally, we present a protocol based on gossiping that uses this hierarchical technique. We present mathematical analysis and performance results to validate the robustness, efficiency and accuracy of the Hierarchical Gossiping algorithm.