Seismic vulnerability analysis of a complex interconnected civil infrastructure - Seismic Risk Analysis and Management of Civil Infrastructure Systems - page 463

18.4.1 Modelling interactions
As shown in Fig. 18.2, a number of association relationships between the
component classes and sub-classes of the infrastructure describe the inter-
actions between distinct systems. Among all possible interactions, the fi gure
shows only those that have been modelled so far. For instance, associations
exist among the InhabitedArea , Network and CriticalFacility classes, but also
between the WSS and EPN classes. The former associations model interac-
tions such as the evaluation of water, power and traffi c demands starting
from population and activities in the urban area, or the determination of
accessibility of damaged buildings or hospitals for the purpose of emer-
gency rescue. The latter are better described in Section 18.5.2.
In a more detailed, lower-level class diagram, such as that in Fig. 18.5,
the above associations, modelling between-system interactions, are shown
between classes corresponding to the actual components that interact with
each other (e.g. interaction between a water pump and an electric substa-
tion through power feeding). At this lower-level within-system interactions,
i.e. the interaction between elements within the same system, are also
visible through association relationships amongst the sub-classes of each
system.
As already discussed in Section 18.3, dependencies should be modelled
with dedicated dependency edges in a super-graph. Correspondingly, a class
should be defi ned for these objects. The attributes of these edges would be
two pointers to the objects they connect and either one or two parameters
(in case of a bi-directional relation) representing the strength of the depen-
dence that can be either deterministic or probabilistic. In the latter case, the
parameter is the probability that the dependent component reacts to an
action of the controlling one (Dueñas-Osorio et al ., 2007). From a compu-
tational standpoint, it is straightforward and much more convenient to
model these edges collectively, rather to include the pointer and depen-
dence-strength parameter as attributes of the dependent object. This is the
reason why dependency edges do not appear in Fig. 18.2 as a separate class
but, rather, as associations between existing classes.

18.5 Description of the main classes

18.5.1 The 'InhabitedArea' class
Buildings, residential, commercial or industrial, make up the largest propor-
tion of the built environment and are the places where we live, work,
consume goods and services. Buildings and the people within them are the
reason for the existence of all other systems. The developed model on one
hand recognises this central role of buildings, while on the other hand, it