Abstract for the talk at 12.11.2013 (15:15 h)VW Seminar
Robin Lamarche-Perrin (MPI MIS, Leipzig)
Macroscopic Analysis of Large-scale Systems: An Approach Illustrated on the Spatiotemporal Aggregation of International Relations
The analysis of large-scale systems faces /syntactic/ and /semantic/ difficulties: How to observe millions of distributed and asynchronous entities? How to interpret the disorder that results from the microscopic observation of such entities? How to produce and handle relevant abstractions for the systems' macroscopic analysis? Our approach is motivated by the following observation: scientific activity relies on /abstraction processes/ that provide macroscopic descriptions to broach the systems' complexity. In particular, in this presentation, we are interested in the production of spatial and temporal abstractions through /data aggregation/. In order to generate scalable representations, the control of two essential aspects of the aggregation process is necessary. Firstly, the complexity and the information content of macroscopic representations should be jointly optimized in order to preserve the relevant details for the observer, while minimizing the cost of the analysis. We propose several measures of quality (internal /criteria/) to evaluate, compare and select the representations depending on the context and the objectives of the analysis. Secondly, in order to preserve their explanatory power, the generated abstractions should be consistent with the background knowledge exploited by the observer for the analysis. We propose to exploit the systems' organisational, structural and topological properties (external /criteria/) to constrain the aggregation process and to generate syntactically and semantically consistent representations. Consequently, the automation of the aggregation process requires solving a constrained optimization problem. We propose a generic algorithm that adapts to the criteria expressed by the observer and we show that the complexity of this optimization problem directly depend on these criteria. The approach is finally applied to the geographical and temporal aggregation of news for the definition of semantically consistent media events and, thus, for the macroscopic analysis of international relations by geographers.