The implementation-service-effect (ISE) metamodel is a general framework for modeling critical infrastructures that can integrate several different perspectives. The metamodel has a technical basis and also provides the abstractions needed for risk assessment and management of critical infrastructures in complex environments. ISE supports an iterative modeling approach that continuously refines models based on new information. By focusing on the services provided by critical infrastructures, the approach bridges the gap between the business and engineering views of critical infrastructures. The technical realization of services is described in the implementation layer of ISE; the effects of the successful (or unsuccessful) delivery of services are described in the effect layer. A sound mathematical foundation provides the basis for analyses ranging from topological evaluations of dependency structures to statistical analyses of simulation results obtained using agent-ba sed models.