Infrastructure Interdependencies - - Infrastructure Characteristics

Infrastructures have four key characteristics that figure in interdependency analyses.

1. Spatial Scales - - Infrastructure can be defined as a hierarchy of elements - - (1) Part, (2) Unit, (3) Subsystems, (4), Infrastructure, and (6) Interdependent Infrastructures.  Spatial relationships are closely related to the notion of geographic scales, given that infrastructures span physical spaces ranging in scale from cities, regions, and nations to international levels.  At the part and unit levels, interdependencies may play only a minor role, if any at all.  On the other hand, deliberations on national energy policies may require analyses at the infrastructure, interdependent infrastructure, national, and international levels, whereas an analysis of he failure of a single natural gas might require studies at the system level and below.
2. Temporal Range - - Time scales have substantial implications for models and simulations, given that certain time-related infrastructure characteristics and interdependencies might not be relevant for a specific analysis.  The tightness or looseness of a specific interdependency is somewhat related to its temporal dynamics and may determine whether that interdependency is pertinent to an analysis.
3. Operational Factors - - How infrastructures react when stressed or perturbed can be a function of operational factors.  These factors are closely related to security and risk and include operating procedures; operator education and training; backup and redundant systems; emergency workarounds; contingency plans including periodic reviews and updates; and security policies, including implementation and enforcement.
4. Organizational Considerations - - Infrastructure systems are subject to a whole host of effects - - from globalization, international ownership, regulation, government versus private ownership, corporate policies and motivations, and the regulatory environment.  These organizational aspects can be key factors in determining the operational characters of infrastructure, with important security and risk implications.