have some shortcomings, including the fact that it in-
correctly assumes that all individuals have the same
contact rate and implicitly assumes that all partner-
ships are infinitely short (Miller et al., 2012; Wang
et al., 2018).
(Miller et al., 2012; Kiss et al., 2017; Wang et al.,
2018) built on these limitations of the mass action
model to introduce the edge-based compartmental
modelling (EBCM) framework. It is a compartment-
based model extension approach where the contacts
between individuals are materialized by the edges
(Miller et al., 2012; Wang et al., 2018). The main idea
is to integrate the heterogeneous mixture by consider-
ing the population as a network of individuals where
the contacts follow a given probability distribution.
Thus, it consists in incorporating into the ordinary dif-
ferential equations of the mass action model, a kind
of social heterogeneity (heterogeneous contact rate),
while taking into account the impact of the partner-
ship duration
2
.
The results obtained from this incorporation have
enabled realistic and more predictable contact struc-
tures to be considered. However, the modification of
the compartmental framework of mass action results
in more and more multiple and complex differential
equations, especially when new concerns (age, sex,
control strategy, etc.) and parameters are taken into
account (Balde et al., 2019). Moreover, another dif-
ficulty of the EBCM framework is that the models it
contains are not easily scalable, extensible and there-
fore not reusable.
Kendrick’s approach (Bui et al., 2016; Bui et al.,
2019) has shown its ability to define concerns (age,
sex, spatial heterogeneity, etc.) as independent (pos-
sibly incomplete) models that are then combined
into stochastic automata networks (SANs) (Plateau
and Stewart, 2000) using a tensorial sum operator.
Stochastic dependencies between concerns are then
introduced in a second phase so that independent con-
cerns can be reused and combined in other models
much more easily. In (Fodjo et al., 2022), the authors
showed that this approach, based on compartmental
models, could be extended to take into account cer-
tain aspects of contact networks while enabling the
building of reusable models. But this generalization
of compartmental models to contact network aspects
is still limited to a few contact networks (Poisson, Ex-
ponential and Scale free).
While it is well known that taking into account as-
pects of contact networks in compartmental models
leads to more realistic and predictive models, there
2
The notion of partnership, materializes here the exis-
tence of a contact (edge), between two individuals. In this
case, we say that these individuals are partners.
is also a large body of work that recognizes the cru-
cial importance of the basic reproductive number R
0
in predicting epidemics (Meyers et al., 2005; Danon
et al., 2011; Molina and Stone, 2012; Heesterbeek
et al., 2015; Zhang et al., 2015; Trapman et al., 2016;
Yang and Xu, 2019). This parameter refers to the
number of new cases caused by a single randomly in-
fected individual in a completely susceptible popula-
tion. When R
0
< 1, epidemics are impossible, while
when R
0
> 1, they are possible. (Aparicio and Pas-
cual, 2007) suggest modifying the SIR compartmen-
tal framework to incorporate the parameter R
0
into the
ordinary differential equations. In this study, in order
to take the aspects of contact networks, R
0
is approx-
imated to Poisson, Exponetial and Scale free contact
networks.
In this work, we propose an attempt to extend
Kendrick’s approach from an approximation of the
EBCM approach while maintaining the separation of
concerns and preserving the simplicity of compart-
mental models. This approximation consists in con-
structing a concern in the sense of Kendrick’s ap-
proach (i.e. as a stochastic automaton that can then
be combined) from the R
0
of each EBCM model. The
extension of the Kendrick approach is done by incor-
porating the base reproduction rate R
0
into the com-
partmental SIR framework. The simulation results
obtained are similar to those of the EBCM configu-
ration model presented in (Miller et al., 2012).
2 MILLER ET AL.’S MASS
ACTION MODEL AND
EDGE-BASED
COMPARTMENTAL
CONFIGURATION MODELS
In this section, and for the purposes of this work,
we will restrict ourselves to the standard mass ac-
tion model of (Miller et al., 2012) and the edge-based
compartmental configuration model.
2.1 Miller et Al.’s Mass Action Model
This model is constructed like the system of Equa-
tions 1) with some modifications. Such as the fact
that the authors of (Miller et al., 2012) assume that an
infected individual causes new infections at the rate
ˆ
βS(t), where
ˆ
β is the transmission rate per infected
Separation of Concerns in an Edge-Based Compartmental Modeling Framework
263