A common theme in analysis and evaluation of network-based critical infrastructure is the assessment of system vulnerability. Graph theoretic, simulation, and optimization-based techniques have played a significant role in examining potential network vulnerabilities given the insights they can provide for mitigating facility loss and prioritizing fortification efforts. Central to these approaches is the concept of facility (arc-node) importance or criticality to system survivability. Assessments of network vulnerability can dramatically differ based on how facility importance is characterized. In this review, various approaches for assessing facility importance and network vulnerability are examined. The key differences in these approaches are the ways in which a facility's role in maintaining network operability is evaluated given arc-node disruption. Comparative results suggest significant differences exist among measures of facility importance and network performance. Furthermore, the subsequent incongruities in these measures and their implications need to be clearly understood to support interdiction risk and vulnerability assessment for critical infrastructures.

Background: While the use of spatially referenced data for the analysis of epidemiological data is growing, issues associated with selecting the appropriate geographic unit of analysis are also emerging. A particularly problematic unit is the ZIP code. Lacking standardization and highly dynamic in structure, the use of ZIP codes and ZIP code tabulation areas (ZCTA) for the spatial analysis of disease present a unique challenge to researchers. Problems associated with these units for detecting spatial patterns of disease are explored.

Evaluating network infrastructures for potential vulnerabilities is an important component of strategic planning, particularly in the context of managing and mitigating service disruptions. Many methods have been proposed to facilitate such analysis, providing different interpretations of infrastructure vulnerability. The primary approaches that have been employed for network vulnerability analysis can be broadly classified as "scenario-specific", "strategy-specific", "simulation", and "mathematical modeling" methodologies. Research on network vulnerability assessment has traditionally focused on one of these methodologies without consideration of the others. This article highlights the important implications of methodology for both infrastructure planning and policy development. To better understand the theoretical and practical trade-offs associated with methodology selection, this article provides a review of these categories of analysis, examining benefits and shortcomings with regard to practical planning issues and policy interpretation. Copyright (c) 2008 Copyright the Authors. Journal compilation (c) 2008 Wiley Periodicals, Inc..

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