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"A system is a construct or collection of different
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elements that together produce results not obtainable
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by the elements alone."
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"A system is a set of elements that work together to produce
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results that the individual elements couldn't achieve alone."
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INCOSE also provides a more specific definition of a 'complex system'
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that emphasises the non-trivial relationships between cause and effect,
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associated its 'emergent' properties :cite:`INCOSE2020`:
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"A complex system is a system in which there are non-trivial
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relationships between cause and effect: each effect may be due
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to multiple causes; each cause may contribute to multiple
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effects; causes and effects may be related as feedback loops,
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both positive and negative; and cause-effect chains are cyclic
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and highly entangled rather than linear and separable."
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This definition of a complex system is particularly relevant to the SIRA modelling framework, as it captures the essence of the interdependencies and interactions that characterise infrastructure systems. The SIRA simulation approach is designed to account for these complexities and provide insights
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into how disruptions from hazards can lead to potentially unpredictable behaviours and propagate through the system, affecting its overall
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functionality.
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The specific meaning of a system and its boundaries depend on the context,
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and it is important to understand how this term is used within the SIRA
@@ -42,56 +57,65 @@ The central idea in the SIRA modelling construct is this:
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All lifeline infrastructure 'systems' within the modelling framework are
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conceptualised as a network of interconnected nodes.
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The 'nodes' or vertices and connecting edges have different meaning based
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on the level of abstraction, which is clarified in following subsections.
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The nodes or vertices, and connecting edges, have different meaning based
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on the level of abstraction, which is explained in following subsections.
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This modelling approach affords a very high degree of flexibility and
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scalability, making it possible accommodate diverse sectors and assets
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of varying scales and complexities.
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This modelling approach affords a high degree of flexibility and
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scalability, making it possible to accommodate multiple sectors and assets
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of varying scale and complexity.
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Furthermore, it allows the user to:
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(a) model the effect of impaired or destroyed components on the
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(a) model the effect of impaired or destroyed components on the
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operational capacity of the overall system;
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(b) use graph theory to assess the graduated capacity degradation, and
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(b) use graph theory to assess the graduated capacity degradation, and
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restoration, through modelling flow through the network; and
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(c) detect prioritised 'paths', or sets of components, within network
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that need to be repaired or restored in order to restore the flow through
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the network which represents the productive capacity of the system.
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(c) detect prioritised 'paths', or sets of connected components, within
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the network that need to be repaired or recovered in order to restore
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the flow through the network which represents the productive capacity
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of the system.
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Terminology in Context: An Infrastructure System
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------------------------------------------------
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Infrastructure System Hierarchy
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-------------------------------
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The elements in an infrastructure (or lifeline) system are conceptualised
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The elements in an infrastructure (or lifeline) system can be conceptualised
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as being structured in a three-level hierarchy:
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**Level 1 : Infrastructure Network --** This is the top level of
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interconnected infrastructure systems where infrastructure facilities are
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connected to form a network or networks.
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connected to form a network or connect to other networks.
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**Level 2 : Infrastructure Facility --** The concept of facilities used in this
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framework map closely to the typology of macro-components as defined in the
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Synerg-G program :cite:`SynerG2010,Pitilakis-etal-2014`, and align with the
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definition systems as defined in :cite:`Rinaldi-etal-2001`.
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**Level 3 : Infrastructure Microcomponent --** This concept of components map
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closely to the typology of micro-components as defined in the Synerg-G program
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**Level 2 : Infrastructure Facility --** Facilities are geospatially discrete
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assets that can be linked to a specific physical location and provide a
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specific service, e.g. a power station or a substation.
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The concept of facilities used in this framework map closely to the typology
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of macro-components as defined in the Synerg-G program
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:cite:`SynerG2010,Pitilakis-etal-2014`, and align with the definition of
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subsystems as defined in :cite:`Rinaldi-etal-2001`.
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systems as defined in :cite:`Rinaldi-etal-2001`.
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**Level 3 : Infrastructure Microcomponent --** These are the physical elements
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that constitute the infrastructure facility, e.g. a transformer or circuit
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breaker within an electrical substation.
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This concept of components map closely to the typology of micro-components as
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defined in the Synerg-G program :cite:`SynerG2010,Pitilakis-etal-2014`, and
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align with the definition of subsystems as defined in :cite:`Rinaldi-etal-2001`.
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This applies to discussions on a *complete* that is responsible for
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This applies to discussions on a complete system that is responsible for
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delivering some service. This also applies to classification of assets,
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and how information about those assets they are stored and referenced
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and how information about those assets are stored and referenced
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in a database.
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Terminology in Context: A Model of a Lifeline Infrastructure
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