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The terms interdependency and dependency are often used in the CIP literature as synonymous. See also dependency.

One of the most cited definitions of interdependency is the one by Rinaldi et al. who define interdependency as a

bidirectional relationship between two infrastructures through which the state of each infrastructure influences or is correlated to the state of the other [1].


European Definitions


This definition is adopted on the Commission's staff working document on a new approach to the EPCIP [2]:

Interdependencies can be identified "between critical infrastructures, industry, and state actors".

The working document also highlights that threats to a single Critical Infrastructure can have "a very significant impact on a broad range of actors in different infrastructures and more widely". The document also highlight the cross-border effect of interdependencies, spanning a number of European countries. The example identified in the document is the European high-voltage electricity grid, composed of the interconnected national high-voltage electricity grids.

European Project Definitions

CIPRNet project

The CIPRNet project [3] uses the following definition:

Interdependency is the mutual dependency of products or services (ACIP, 2003).

National Definitions


Inter-dependency is the series of supply-orientated relationships that exist between distinct systems that, when altered, affect their continued operation. [4]

New South Wales
Interdependency: When multiple critical infrastructures rely on each other for continued service provision. [5]


Interdependência: relação de dependência ou interferência de uma infraestrutura crítica em outra, ou de uma área prioritária de Infraestruturas Críticas em outra. [6]

Interdependence: dependency relationship or interference of a critical infrastructure with another, or of a Critical Infrastructure priority area with another.


Interactions or mutual influences between different Critical Infrastructures. [7]

An older definition was:

Interdependency is the complete or partial mutual dependency of several goods or services [8].


Interdipendenza: relazione funzionale tra due sistemi o infrastrutture attraverso la quale lo stato di ogni infrastruttura è correlato allo stato dell’altra, influenzandolo ed essendone reciprocamente influenzato. [9]

Republic of Trinidad & Tobago

Mutually reliant relationship between entities (objects, individuals, or groups). [10]

The degree of interdependence does not need to be equal in both directions.


Interdependencias: los efectos que una perturbación en el funcionamiento de la instalación o servicio produciría en otras instalaciones o servicios, distinguiéndose las repercusiones en el propio sector y en otros sectores, y las repercusiones de ámbito local, autonómico, nacional o internacional. [11]

United States

Interdependency. Mutually reliant relationship between entities (objects, individuals, or groups); the degree of interdependency does not need to be equal in both directions. [12]

Mutually reliant relationship between entities (objects, individuals, or groups). [13]
The degree of interdependency does not need to be equal in both directions. For example, the Energy Sector depends on a functioning Water Sector for successful day-to-day operations, just as the Water Sector needs energy to effectively manage water and wastewater systems [14]


Empirical analysis of Critical infrastructure incidents and events by Van Eeten et al. shows that interdependencies (= the mutual Dependency) hardly occur; and when they occur the effect is at a lower (weaker) dependency level.

See also