Modelling Multi-Agent Systems
with Organizations in Mind
Matthias Wester-Ebbinghaus and Daniel Moldt
University of Hamburg, Department of Informatics
Vogt-K¨olln-Straße 30, D-22527 Hamburg, Germany
Abstract. Software systems are subject to increasing complexity and in need of
efficient structuring. Multi-agent system research has come up with approaches
for an organization-oriented comprehension of software systems. However, when
it comes to the collective level of organizational analysis, multi-agent system
technology lacks clear development concepts. To overcome this problem while
preserving the earnings of the agent-oriented approach, this paper propagates
a shift in perspective from the individual agent to the organization as the core
metaphor of software engineering targeting at very large systems. According to
different levels of analysis drawn from organization theory, different types of or-
ganizational units are incorporated into a reference architecture for organization-
oriented software systems.
1 Introduction
Modern software systems are subject to ever increasing size and complexity. Within the
IT community the expectation begins to form that the sheer size and speed of growth
of these systems render most traditional software engineering approaches (relying on
a top-down design, expecting comprehensive knowledge of relevant system-wide pa-
rameters, based on the possibility of applying a central control facility) inept [16]. It is
these software systems in the large that the article at hand is devoted to.
Multi-agent systems as a software engineering paradigm are one candidate to pro-
vide solutions for this kind of systems. Exemplary in [11], Jennings argues that multi-
agent systems are very well suited for the realization of three particularly important
techniques for handling complex software, namely decomposition, abstraction, and or-
ganization. At the same time however, Jennings calls for a social level view on multi-
agent systems in order to deal with the difficulties that agent autonomy and sophistica-
tion in combination pose on the prediction of the overall system behaviour by leading
to a considerable scope of emergence.
In subsequent years until today various approaches have been brought forth that are
in line with this request by taking the perspective on a multi-agent system as an organi-
zation (an overview of recent and current work can be found in [19]). Noteworthy, the
rationale for adopting an organization-oriented perspective throughout the approaches
mostly refer to the very same features that Hannan and Carroll identify as the main
capacities of organizations in human societies: Organizations are durable, reliable and
Wester-Ebbinghaus M. and Moldt D. (2008).
Modelling Multi-Agent Systems with Organizations in Mind.
In Proceedings of the 6th International Workshop on Modelling, Simulation, Verification and Validation of Enterprise Information Systems, pages 81-90
DOI: 10.5220/0001737900810090
accountable [10].
In this respect, organization-oriented approaches to multi-agent sys-
tem engineering seek to combine local agent autonomy with the assurance of global
system characteristics by imposing ”organizational facts” onto the system. Boissier [3]
identifies different organizational dimensions (with structural, functional and interac-
tional dimensions as the most prominent ones) that receive varying emphasis depending
on the particular approach.
However, when relating multi-agent system approaches to organization theory it
becomes obvious that the true potential of the organizational metaphor is not entirely
exploited. Multi-agent system research so far has mainly focussed on the conception
of organizations as contexts for individual agents. As we have analyzed in [19], the
importance of organizations as corporate actors that Scott [18] stresses for more global
(ecological) levels of analysis has been largely neglected.
Consequently, the long term goal of our work is the provision of a software de-
velopment approach that builds upon and extends the multi-agent system approach in
order to account for the true potential of the organizational metaphor. In this paper we
supplement this goal by proposing an abstract reference architecture for organization-
oriented software systems. Ferber [8] advances the distinction between ACMAS (agent-
centred multi-agent systems) and OCMAS (organization-centred multi-agent systems).
We consider our approach as one further step in this shift of paradigm from agent- to
organization-orientationand term the systems introduced by our approach MOS (multi-
organization systems).
In Section 2 we present our approach of modelling open and controlled system
units. We utilize the introduced universal scheme to propose a reference architecture
for multi-organization systems composed of concrete organizational units in Section 3.
We conclude our results and provide an outlook to future work in Section 4.
2 Open System Modelling
The introduction should have made clear that the software systems addressed here are to
be comprehended as systems of systems. To arrive at an illustrative modelling approach
despite the inherent complexity of the systems in focus we adopt the modular view of
each system as a unit that maintains relationships to other system units. As a prelimi-
nary step to dealing with particular types of system units in our organization-oriented
architecture, this section refers to system theory in order to introduce a general model.
2.1 Basic System Unit
Most of the important entities studied by scientists nuclear particles, atoms, molecules,
cells, organs, organisms, communities, organizations, societies, solar systems come
under the category of a system [2]. Consequently, the characterization of a system fol-
lows quite abstract as an assemblage or combination of parts whose relations make
them interdependent.
It will not be discussed in this paper that each of these capacities is a double-edged sword and
not all organizations measure up to them.
add remove
use / modify
internal system parts
Fig.1. An Abstract View on System Units.
Based on this abstract characterization, Figure 1 shows a general model of system
The evolution of the overall system unit solely depends on its internal parts, whether
new parts are added (add), former parts are removed (remove) or current parts are used
and potentially modified (modify / use). The details of these operations and how they
come into being depend on the characteristics of a particular system.
2.2 Recursive Nesting
The basic model of system units of the former subsection emphasizes the similarities of
all types of systems. However, there exist of course substantial differences between par-
ticular systems. Exemplary, Boulding [4] presents a typology of systems that advances
from physical over biological to social systems. Along the way, each successive system
becomes progressively more complex, more loosely coupled, more dependent on infor-
mation flows, more capable of self-maintenance and renewal, more able to grow and
change, and more open to the environment.
Especially the openness to the environment is of particular importance regarding
the software systems this paper addresses. Systems of systems implicate a network of
relations where each system (to different degrees) relies on the services and resources of
other systems. Interactions with the environment and throughput of external resources
are regarded as crucial for the functioning and self-maintenance of open systems [17,
5]. Nevertheless, open systems have boundaries and spend energies to maintain them.
Consequently, one can identify the twin properties of open systems as consisting of two
basic (and opposing) sets of system processes [5]. The term morphostasis refers to those
processes that tend to preserve or maintain a system’s givenform, structure, or state. The
term morphogenesis refers to processes that elaborate or change the system. While both
are not exclusive to open systems they receive a special emphasis. In adapting to the
external environment, open systems typically become more differentiated in form and
more elaborate in structure.
It is not very helpful to regard the environment of an open system as simply ”ev-
erything else”. It suggests itself to comprehend the environment again as a system (or
multiple systems) and thus to arrive at a recursive understanding of open system models
as for example explicated by Koestler’s concept of a holon [12] and in Beer’s recursive
model of viable systems [1]. Each open system is characterized as ”Janus-faced” with
The model has a coloured Petri nets semantics, cf. [9].
Fig.2. System Unit with Coloured Internal Parts.
an inner eye at the internal systems and an outer eye at the surrounding system (or sys-
tems). Here, our perspective on systems as units leads to an illustrative understanding.
The relation of open systems to their environments is traced back to the (not necessarily
unique or disjoint) nesting of system units, the embedding of system units inside other
system units.
We use this short summary of system theoretical inspirations to refine our model
of system units. The first step is a colouring of the internal parts of a system unit as
shown in Figure 2.
The internal parts are now explicitly to be regarded as system units
themselves. The colouring is no partitioning, the different sets of internal units need not
be disjoint. It is more of a conceptual classification according to function.
The operational units are those parts of the system in focus that undertake the sys-
tem’s primary activities. In a manufacturing setting they would be the production units,
teams of people, and machines that actually do the manufacturing. In a complex pro-
duction organization they would include manufacturing, distribution, and warehousing.
Basically, the operational units are the intrinsic parts of the system.
The integrational units see to it that the singular operational units are integrated into
a joint system in the first place. They define the means by which the operational units
may participate in the system and regulate their activities. One example is the nervous
system of the human organism that connects the muscles and organs (being operational
units). In another setting, they embody hierarchical planning and performance control
systems of an enterprise.
Governance units are responsible for certain system processes and structures being
in place, to ensure the adherence to system laws, and to maintain mechanisms for con-
trol and coercion. One example is the brain of the human organism that oversees the
complex of muscles and organs and tries to optimze them. It also establishes a connec-
tion to the environment through its senses. It plans, projects and develops an identity.
The transitions connecting to the outer circle are just short forms that include all three cases
for the inner circles respectively. To obtain a well-formed Petri net model the short forms have
to be resolved, resulting in a total of nine transitions for Figure 2.
Another example is the board of directors of an enterprise that sets the goals and strate-
gies, determines the budget and establishes connections to core business partners.
A clear separation between the different types of internal system units is not always
possible just as it is not always clear where to locate morphostasis and morphogenesis.
For example,in one system the purposeof the governanceunits might be to just preserve
and maintain a set of largely fixed system laws. In another case, the government units
might be a continuous source of major renewal.
Generally speaking, the distinction serves to carry out separation of concerns in two
ways. Firstly, the administrative units are distinguished from the operational units that
they embed. Secondly, technical embedding (via the integrational units) is distinguished
from strategical embedding (via the governance units).
2.3 Structure in Threes
The overall behaviour of a system unit manifests in various system processes that shape
and evolve the system. In order to study these processes exhaustively, we identify no
less than 27 case distinctions that stem from three orthogonal dimensions with three
values respectively.
Operation: The three basic operations that a system process may relate to are add,
remove, and use/modify.
Direction: System processes may impact the system from three conceptual direc-
tions. The operational units (enabled by the integrational units) impact the system
from below. The maintenance units impact the system at the same level. Finally,
surrounding system units may impact the system in focus from above.
Affected internal system unit: Each system process may involve all three kinds of
system units, operation, integration, and governance.
The details of each case and whether it is of relevance at all depend on a particu-
lar system. Consequently, there is no point in addressing each individual case for our
general model of system units. Instead, we provide coarsened models for the three di-
rections that summarize multiple cases of the other two dimensions.
Figures 3 - 5 show the influences on the system from below, at the same level,
and from above through the integration of operational units, controlling activities by
governance units and peripheral connections to surrounding system units respectively.
To obtain a modelling for each of the 27 cases the first step is to refine the transitions
that connect to the outer circle of the system unit in focus. In addition, the three cases
shown here are somewhat ”pure” cases. In particular systems they are typically merged.
3 Reference Architecture
The refined model of open system units still does not offer a meaningful architectural
model for IT systems. It lacks differentiation for particular perspectives. The central
concern of this section (and the overall paper at hand) is to advance a proposal for
software architectures in the large based on the universal scheme of open system units
and their embedding inside each other.
offer frame
Fig.3. Open System Unit: Integration Processes.
Fig.4. Open System Unit: Governance Processes.
The modelling of complex systems requires different levels of abstraction. The con-
tents at each level should be described in a way that offers a largely complete and
homogenous picture of the selected perspective for this level of abstraction. From this
premise we derive our architectural proposal for multi-organization systems.
3.1 Overview
In focussing on the organization as the core unit of the architecture, three necessary
levels of examination directly follow: The organization itself, its internals and its envi-
ronment. The architecture shall include multiple organizations and each of these may
have different (conceptual) environments. It follows the necessity of a fourth architec-
tural level as a system closure for the integration of all environments.
Interestingly, this identification of four levels resulting from rather technical consid-
erations is confirmed by organization theory according to Scott [18]. The internals of
an organization correspond to the socio-psychological level of organization theoretical
analysis where the behaviour and relations between individual members of the organi-
zation is examined. From this perspective, organizations are regarded as contexts. The
organization as a discrete entity of its own appears at the organization structure level
use frame
Fig.5. Open System Unit: Peripheral Processes.
where the structural properties and social processes that characterize an organization
and its subdivisions are studied. The ecological level finally focuses on characteristics
and actions of organizations as corporate actors that operate in even more global net-
works of relations. For the ecological level, further refinements are possible. Among
these the concept of organizational field is the most comprehensive one referring to
immediate environments of organizations while the society offers a common frame for
organizational fields.
As a consequence, our reference architecture for multi-organization systems con-
sists of four levels of system units. In order to emphasize that these units are particu-
lar instances of the universal scheme of system units according to Section 2, they are
termed organizational units. Figure 6 shows an overview of the architecture as nested
organizational units.
Each department is exclusively assigned to an organization. Each organization
consists of multiple departments and operates on multiple organizational fields. Each
field hosts multiple organizations and is embedded in the single integrative society.
Departments as the lowest level units of abstraction embody the connection to multi-
agent system technology. Each department is a multi-agent system. This perspective
only makes sense if a department fulfils an organizational purpose. As described in the
introduction of this paper, a considerable part of multi-agent system research of the past
years was devoted exactly to this aspect. Thus, we arrive at a seamless transition from
agent- to organization-orientation. All organizational units of the reference architecture
can be regarded as logical units (nevertheless embodied by explicit software constructs,
e.g. being agentified) that are built upon physical multi-agent systems.
This distinction according to Scott is a refinement of the prevailing distinction in micro- and
macro-level where the first corresponds to the social-psychological level and the latter encom-
passes all other levels.
The model has a reference net semantics. Reference nets show some extensions compared to
conventional coloured Petri nets [14]. They implement the nets-within-nets paradigm where a
surrounding net (the system net) can have nets as tokens (the object nets). Reference semantics
is applied, so these tokens are references to net instances. Synchronous channels allow for
communication between net instances.
positions +
Fig.6. Multi-Organization Software Architecture: Overview.
3.2 Architectural Levels
Due to space limitations, no complete description of the architectural levels is possible
in this paper. Instead, we present a short summary of the characteristics of each level in
order to sketch the conceptual differences.
Society. The society as the highest architectural level embodies the closure of the
system and thus has no super-ordinate units. It embeds organizational fields. These
are connected through a field infrastructure for interaction and migration between
fields. The government is a legal authority that holds and enforces system-wide
(field-spanning) societal laws.
OrganizationalField. DiMaggio characterizes organizationalfields as critical units
bridging the organization and society level in the study of social and community
change [7]. For example, state regulations directed at individual organizations are
typically mediated by field level structures such as trade associations.
Concerning the characteristics of an organizational field, two broad categories are
distinguished. The material-resource structure characterizes the field as a stock
of resources and source of information, which provide the primary premise under
which organizations as inhabitants of the field come together. However, material-
resource environmentsalways rest on an institution. As Scott puts it, institutions are
composed of regulative, normative, and cultural-cognitive elements that together
with associated activities and resources provide stability to social life [18].
Organization. Organizations put particular emphasis on an organizationalstructure
and an organizational authority. Mintzberg [15] for example identifies five funda-
mental types of organizational subdivisions (operating core, middle line, strategic
apex, technostructure, support staff) that are integrated into an organizational su-
perstructure. It is built up by grouping individual positions into units and units
into ever larger units until the hierarchy is complete.
Each organization has an authority that is in charge of power and setting the or-
ganizational goals. Cyert and March [6] come up with a quite broad concept. Or-
ganizations are viewed as being composed of various and varying coalitions, each
of which seeks to impose its preferences onto the larger system. If none of them
succeeds, they seek as allies other coalitions whose interests are related. Finally, a
conglomerate will arrive at a mutually acceptable agreement and at the same time
will be influential enough to constitute the dominant coalition of the organization.
Department. The requirement of departments being exclusively assigned to orga-
nizations is a logical one. Departments of different organizations need not be dis-
joint and might for example acquire their members from the same physical multi-
agent system. Nonetheless, it is crucial to distinguish between different depart-
ments. This issue has been addressed by multi-agent system technology and cor-
responding solutions follow the common organization implementation architecture
for open MAS from [3]. The integrational units as positions and grouping charac-
teristics represent an organizational layer that encapsulates organizational specifi-
cations. This layer offers proxies to which domain agents from an open multi-agent
system must connect to act as members in the organization.
Supervision and authoritarian decision making might be woven into the position
and grouping specifications or might instead (or additionally) be taken care of by
an explicit management.
4 Conclusions
We have presented an extended perspective on current organization-oriented multi-
agent system engineering and derived a reference architecture for multi-organization
systems. The architecture introduces four types of (logical) organizational units built
upon (physical) multi-agent systems.
The rationale for the selection of the particular organizational units of the archi-
tecture is deeply rooted in organization theory. The result is a software engineering
approach that supports micro as well as macro perspectives and at the same time is ac-
companied by concepts and constructs that are familiar from real-world social scenar-
ios. In this respect, our proposal is also one step in the direction of supporting a proper
IT alignment through a homomorphism between real-world and software artefacts.
As a related aspect, we consider our approach to be multi-perspective. One partic-
ular software system might appear in multiple instances of multiple types of organiza-
tional units at the same time. It all comes down to embedding relations. For example,
one software system might relate to a second one like an organization to a field and to
a third one like a department to an organization (virtual organization).
Turning to future work, the practical usage of the architecture is the most pressing
issue. As a starting point, a Petri net-based model of organizational structures and ser-
vices is presented in [13]. At the same time it is demonstrated how agent technology
can be used as a middleware to deploy the organizational specifications. The modelling
approach is general enough to be adapted for arbitrary levels of abstraction and allows
to define collective entities and nest them inside each other. Thus it supports the devel-
opment of multi-level architectures.
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