A Design and Preliminary Evaluation ofHierarchical Organizational Behaviour Modelling Architecture
Kensuke Kuramoto 1, Masakazu Furuichi 1
11

Graduate School of Industrial Technology, Nihon University, Japan

Introduction

In the field of large scale multi-agent based simulations,such as war game simulations for defence or disaster
simulations, a simulation program has to control huge numbersof entities such as soldiers, rescues, civilians or a variety ofvehicles which are expected to run autonomously. However,since the current multi-agent schemes are not enough powerfulto achieve fully autonomous agents required for training
simulation systems for war game or disaster simulations, human
support at runtime is required. Such human is called a response
cell, and many response cells are required for large scale
simulation in order to control the behaviour of hundreds ofentities by input their routes, movement or actions in details.
Same situation happens for scenario preparation, as thesimulation scale grows, the effort of scenario input increases
drastically, which becomes a critical issue.
Therefore, new methods are required to reduce the numberof response cells, or the increase of the efficiency of scenario
input. For instance, in a conventional method, response cells
have to provide all required information for all entities. Our
proposal is based on the idea to introduce such mechanism that
response cells provide only macroscopic inputs, such as theobjective of the entities, and the system expand them tomicroscopic orders or commands. However, when the numberof entities becomes huge, even providing macroscopic inputs is
also difficult by the limited number of response cells.
In order to solve the above problems, we propose thearchitecture for hierarchical organizational behaviour modelling(HOBM). Using HOBM, entities are structured as organization,and they behave by the orders given by the leaders. Leadersgather information reported from their members, and they giveorders to their members. Moreover, a leader is also a member ofa super leader, and a super leader is also a member of the boss,and so on, this hierarchical architecture ensures the scalability ofthis model. By introducing HOBM, the efficiency of scenario
input may be increased at preparation phase, and also we canreduce the number of response cells at run time.
In this paper, we will describe the overview of our proposed
HOBM, and also a preliminary evaluation results are shown.
2

research of [2], it employs leaders for efficient building
evacuation, but since the leaders are not hierarchically organized,
it is not scalable.
On the other hand, our proposed HOBM architecture isbased on the idea that organization is hierarchically structured,and the role of each level of hierarchy is different. Moreover, thehierarchical structure of HOBM is recursively organized, it canbe applicable to large scale real-world organizational behaviourmodelling.
As the Fig. 1 shows, the objective of the organization isshared by the highest leader (the boss), super leaders and leaders.
Therefore, those leaders give commands to their subordinate toachieve the objective, by deriving concrete orders such as move,sense, act or others from a more general objective. In order thatthose leaders derive concrete orders, members give report totheir leader. In the same way, leaders give report to their superleaders, and super leaders give report to the boss.
In [2], it employs leaders and leaders teach information of
the environment to the members, but leaders have to own
complete information of the environment at runtime, andmembers do not give reports to their leader, and this point isdifferent from our method. In HOBM, reports from subordinates
are the essential to the leader’s decision process.

HOBM Architecture

An organization can be defined as a set of members, and amember belong to a sub-group of an organization which has one
leader. A leader is a member of another sub-group, and a thissub-group has a super leader. This hierarchical structure iscomposed recursively (Fig. 1). As the figure shows, top of theorganization is called the boss, and all the members of thisorganization behaves based on the common objective of theboss.
In previous research, “Group Model (GM)” is proposed andfocused for group behaviour modelling, and it is applied tocrowd models for evacuation [1, 2, 3]. However, in GM, groups
are considered to be uniform, and mass of entities behaves asgroups, but the behaviour models of all are equal. In theFig. 1. Organization
2.1 Objectives and Commands
Each level of leaders, including super leaders or the boss
have their objectives, and they are spread to their subordinates
through commands. Commands are generated in a manner thatan objective is break down to more concrete commands.
Therefore, all members of the organization share the sameobjectives. The command to the boss is given from outside of
the organization, but it’s usually given as a scenario by a person
who executes that simulation.

2.2 Information Feedback
Members of an organization communicate each otherthrough their leader. Subordinates of organization give theinformation to their leader through reports (Fig. 1), and theinformation includes environment, detected other agent, andtheir own status. The leaders derive decision using thisinformation given from the subordinates.
2.3 Recursive Structure
The proposed HOBM architecture is inherently recursivestructured. Therefore, as the Fig. 1 shows, the relation between
leader and member is same as that between leader and superleader, and super leader and a boss. It means that we can able toexpress a small platoon model, to a huge legion model. As thesize of an organization increases, by increasing the level ofrecursion, we can ensure the scalability of this HOBM.
3Preliminary Evaluation of HOBM

In order to show the effectiveness of HOBM, we have built
a prototype system which simulates a simple evacuation model
shown in Fig. 2. We have used “Artisoc” which is a tool tomodel and simulate multi agent simulations.

Fig. 3. Crowd Map

3.2 Result of the Experimentation
The result of the experimentation is shown in Table 2. In thetable, the number of iterations that all or half evacuees
completed their evacuation is shown. We ran the test cases in 20
times and the averages are shown in Table 2.
As the table shows, result of the case 1 (with leader) is better
than that of the case 2 (without leader). It implies theeffectiveness of the leadership.

Table 1. Parameters of the Test
Length of Building
Radius of Each Evacuee
Length of Eye Sight
Width of Paths
Number of Evacuee
Number of Trials of the Simulation

50m
0.4m
2m2m5020

Table 2. Result of the Test
Average Iterations of All
Evacuees EvacuationFig. 2. A Screenshot of Evacuation Simulation for aPreliminary Evaluation
Without Leader
With Leader

3.1 Experimentation
In this evacuation model, we assume that entities escapefrom a building, which has several evacuation routes.
The building has walls and paths, and the routes of evacuees
are blocked by walls. The rule of evacuees’ movement is ruled
by Helbing’s equation[1] which are characterised that theyreceive forces from walls and other evacuees.
Although all evacuees would like to escape toward the exitof the building, information that they can get is limited, since
their length of eye sight differs. In this preliminary experiment,
the length of the building is 50m and the eye sight length ofevacuees is 2m. Parameters of the test are shown in Table 1.
In this experimentation, each evacuee’s own behaviourmodel is very simple. They run toward the exit and if they bumpinto wall, they follow wall by right-hand or left-hand rule until
the end of the wall.
We evaluated and compared two cases. One is with a leader,
and the other is without a leader. In both of the cases, number of
evacuees in the simulations is 50.
In the case with a leader, subordinates send their sightinformation to their leader and the leader make crowd map
which is shown in Fig.3. In order that the leader tries to avoid
collision of evacuates, the leader refers to the map and sends acommand to his subordinate to move to the less crowded
direction. When they do not get commands from the leader,evacuees decide to move only by their own information.

41119
1101

Average Iterations ofHalf Evacuees
Evacuation
740
722

Conclusion

We proposed the HOBM architecture, a new method which
is applicable to modelling hierarchical organizational modellingfor a large scale simulation. Our preliminary evaluation result
implies that the effectiveness of the leader which sends
commands to the subordinates and receives information byreports for their decision making. In this preliminary result, wehave not showed the effectiveness of this recursive structure,and this is our future work. We also need to evaluate this using
more complex scenario and larger scale problem, to show theeffectiveness of this method to the real world problems.
References[1]
[2]

[3]

D.Helbing et.al, “Simulating Dynamical Features of EscapePanic” , Nature, Vol. 407, pp.487-490, 2000
N.Pelechano et.al, “Modeling Crowd and Trained Leader Behavior
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S.Yamakage, “ Jinkou Shakai Kouchiku Shinan (How to Build an
Artificial Society)”, Shoseki Kobo Hayakawa, Japan, 2010