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belief-content
which specifies the conditions of that belief [28]. The library
allows for multiple beliefs of the same type. A set of agent intentions are implemented
as a stack and consist of
intention-name
and
intention-done
, which speci-
fies the condition by which that intention is completed [28].
In the ABM, communication between agents is managed by a message passing li-
brary accompanying the BDI library for Netlogo [29]. In this way, social networks
can be simulated which communicate information that influences decision-making
and behaviour. For example, members of the same clan will communicate the condi-
tion of their current patches to each other to allow informed decisions about moving
to new locations.
4.4
Building the ABM
In this initial version of the ABM, herder agents make decisions under certain condi-
tions while pursuing their common goals. These decisions are implemented as sets of
intentions and modified by their beliefs. According to the overarching goals identified
in the previous section, herder agents execute the intention to
subsist
on a daily
time-step, which includes more specific intentions to
find-grass
, to
graze
and
to monitor the condition of their herd.
The second overarching goal is implemented as an intention to
cope-with-
stress
. Under this intention, a more specific intention to
assess-location
is
executed in particular months, as identified from the seasonal decisions identified in
the qualitative data analysis. Agents score their current patches against the patches of
ten random herders in their social network according to a set of identified criteria,
including the relative condition of the 11 patches, the number of cattle in and neigh-
bouring each of the patches, a preference to stay in their current locations and a prefe-
rence to move to their home locations in the wet season months. When the score is
received (
intention-done
), an agent will either remain in the current location or
move towards a new one.
Decisions about coping with environmental stress depend on agent beliefs about
rainfall. For example, in the dry season (March-June) herders will continue to execute
the intention to
cope-with-stress
until it rains for a consecutive number of
days (which is the
intention-done
condition) after which they will continue to
subsist
until the next intention is triggered off the stack. Strategies for coping with
stress depend on agent beliefs. For example, more
traditional
agents will follow
a set of intentions based on customary coping mechanisms including
split-herd
,
reduce-herd
,
osotua
and
mix-species
. If these strategies for coping with
stress fail, beliefs may be modified and something else will be attempted. Agents that
have pre-determined or adapted
commercial
beliefs will be more likely to
sell-
cows
and to
diversify
their activities to
cope-with-stress
.
The goal to maintain socio-cultural functions is more complex and includes inten-
tions such as maintaining social networks which play an important role in pastoralist
societies, including the Maasai in Kajiado. Social networks are crucial in maintaining
mobility, surviving shocks and stresses and gathering information about natural re-
sources, cattle prices and so on [30]. For example,
osotua
is represented in the ABM
