Information Technology Reference
In-Depth Information
For the choice of a message, the selection value
V
m
sent
is calculated for each answer
m
sent
∈
=
INFORM. Starting with the highest selection value, the
messages are processed in descending order. As long as the supplier's inventory stock
level allows for fulfilling the processed order, an INFORM message is sent. If that is no
longer possible, all subsequent orders are refused.
M
with
perf
(
m
sent
)
5
Empirical Evaluation
In order to validate the ability of expectation-based self-organization to efficiently struc-
ture and operate multiagent systems modeling supply networks, that approach will be
compared to the performance of a system with a previously defined communication
structure. For this purpose, the approach is implemented and applied to an example
scenario using the multiagent-based simulation system PlaSMA [20].
5.1
Experimental Setup
In this evaluation, a network with three tiers and three parallel operating entities is
modeled as depicted in Figure 3. Each agent produces and/or consumes an amount of
two units of the product types A and/or B (two A being transformed into two B by the
agents at the manufacturing tier). Furthermore, every agent has an outbound inventory
capacity of four units per product type, restricting the amount of goods that can be
produced and stored by a single logistics entity. The agents acting as customers pursue
a policy of ordering an amount of four units if the respective inventory stock level
reaches six or less.
In the simulation, a message sent by an agent can be received and processed in the
next time slice at the earliest. Therefore, sending an order and receiving the response
takes two simulation cycles. In that time, four units of the required type of products can
be consumed. Thus, the chosen order batch size enables maximal utilization of produc-
tion and consumption processes while requiring minimal outbound storage capacity on
the suppliers' side. However, the threshold of six units for placing an order enables the
agents at the manufacturing tier to build up inbound safety stocks, allowing for contin-
ued production in case of supply shortfalls and thus compensating disturbances at the
early network tiers.
Knowing these mentioned capabilities of the participating agents, it is easy to pre-
structure this network by choosing an arbitrary bijection out of the possible relationships
between each two tiers. For each order following the mentioned policy, this ensures the
number of receivers being one (the possible minimum) and the supplier to be able to
fulfill that order as soon as enough raw material has been produced in an initialization
phase (as the amount of consumed goods equals that of produced ones). Thus, such
an arrangement of relationships necessarily leads to a maximized operation efficiency
of the modeled supply network using a minimal number of sent messages. Regarding
these objectives, it therefore guarantees optimal results making it especially suitable as
a reference for the self-organizing approach.
However, without prior knowledge of other agents' capabilities and relationships,
the choice of interaction partners leading to an efficient and reliable network structure
