=Paper= {{Paper |id=None |storemode=property |title=A UML-Based Notation for Representing MAS Organizations |pdfUrl=https://ceur-ws.org/Vol-741/ID20_CossentinoLodatoLopesRibiniSeiditaChella.pdf |volume=Vol-741 |dblpUrl=https://dblp.org/rec/conf/woa/CossentinoLLRSC11 }} ==A UML-Based Notation for Representing MAS Organizations== https://ceur-ws.org/Vol-741/ID20_CossentinoLodatoLopesRibiniSeiditaChella.pdf

A UML-Based Notation for Representing MAS
Organizations
Massimo Cossentino∗ , Carmelo Lodato∗ , Salvatore Lopes∗ , Patrizia Ribino∗ , Valeria Seidita† , Antonio Chella†

∗ Istituto di Reti e Calcolo ad Alte Prestazioni,

Consiglio Nazionale delle Ricerche,
Palermo, Italy.
Email: {cossentino, ino, toty, ribino}@pa.icar.cnr.it

† Dipartimento di Ingegneria Chimica Gestionale Informatica Meccanica

Università degli Studi di Palermo
Email: {seidita, chella}@dinfo.unipa.it

Abstract—A notation for representing agents’ organizations to methodologies for MASs where some aspects of organization
be implemented using Moise+ and Jason is proposed. For this were modeled. In one of the most known in literature [7] the
purpose a UML profile was defined for representing the elements concepts of environment, roles, interactions and organizational
of Moise+ organizational model such as role, mission and group.
The proposed notation will be fully illustrated and applied to the rules are taken into account as organizational abstractions.
classical example provided by the J-Moise+ team. Another example has been proposed in [8] where holarchy
represents the organization structure of the MAS made of
holons [9] hence the main element to be developed for building
I. I NTRODUCTION
the MAS organization.
In the context of highly complex, distributed and open The work illustrated in this paper regards the creation of
systems, engaged and working in dynamic environments are a specific notation for representing the organizational model
widely employed. Such system should include the capabil- proposed by Moise+. The advantages of having a graphical
ity of continuously reacting, with a re-organization process, notation for representing organizations are evident: first of
to changes occurring in the environment. Because of their all, graphical notations are more readable and understandable
intrinsic nature, agents have been recognized to be a good at a glance than any coding language, secondly it is usually
way for solving complex problems both at the design and the easier to explain a graphical notation to stakeholders involved
implementation levels [1] [2]. in the designer (that are not designer) than read the application
Organizations [3] play a relevant role in multi-agent systems code with them. The possibility of involving stakeholders like
design; they can be seen as the set of constraints ruling the system users enables the adoption of agile or extreme develop-
agent’s behavior in multi-agent systems (MAS from now on). ment approaches and improves the flexibility of conventional
As regards the agent organization implementation, a robust ones.
approach coming from Hubner et al. [4] proposes an orga- The remainder of the paper is organized as follows. In
nizational model (Moise+) able to support the re-organizing section II the Moise+ organizational model, J-Moise+ and
process of MAS. Moise+ describes the organization in a MAS Jason are introduced. In section III we explain the proposed
by employing three main views: the structural, the functional notation by using three kinds of diagram in order to define
and normative specifications. In this model an organization graphically the structural, functional and normative specifica-
is established a priori (created at design-time) and the agents tion of a Moise+ organization. In this section an instance of the
ought to follow it. The Moise+ organizational model considers notation in use by using the Moise+ tutorial [10] example for
the structural and functional dimensions as almost independent generating the three specification diagrams is also provided.
while the normative dimension is used to establish a link Section IV offers a comparison with others MAS modeling
between them. proposals. Finally some discussions and conclusions are drawn
The Moise+ organizational model is complemented with in section V.
the possibilities of quickly and easily programming MAS by
II. BACKGROUND
means of J-Moise+ [5], a Jason extension allowing developers
to use Jason for programming agents and their organizations A. Moise+
[6]. Moise+ [11][4] is an organizational model for MAS looking
This offers a powerful tool to MAS developers, nevertheless at organization from three different perspectives: structural,
it is not still adequately supported by a well defined method- functional and normative. From the structural viewpoint, an
ological approach. Some researchers in the past developed organization can be seen as a set of Roles linked by Relations
and clustered into Groups. Analyzing an organization from the A. Organizational Diagram
functional perspective allows designers to define the global The Moise+ structural specification defines the available
objective, and also the plans and the way for reaching this roles, groups, and relations between these within the MAS
goal by means of a Social Scheme. In this scheme the func- organization. Using the normative specification we can con-
tionalities of the organization are represented as Goals grouped strain the agents behavior by specifying what missions an
into Missions. Finally, modeling the normative aspect of the agent ought to follow and what missions an agent is allowed
organization allows to assign a mission to a Role by means to follow when playing certain roles.
of Permission or Obligation norms. Norms can be seen as the
We use a UML class diagram (named Organizational
backbone connecting the functional and structural aspects of
Diagram OD) for representing the structural and normative
an organization.
specification. The Organizational Diagram focuses on Moise+
While the Moise+ implementation is based on two key elements such as Group, Roles, Missions and different kinds
elements: the Organizational Specification (OS) that is the of relationships.
union of structural, functional and normative specification and The development methodology of an organization with
the Organizational Entity (OE) that is the instantiation of OS Moise+ is out of the scope of this paper, but in order to
on a set of agents. understand this diagram we can say that the building of this
diagram is subdivided in two phases. During the first phase
B. Jason
all elements concerning the Moise+ structural specification
The development of cognitive agents can be based on are established, while the second phase starts at the end of
different approaches [12]. Jason approach is based on the the definition of the schema structural diagram and it aims
BDI (Belief-Desire-Intentions) architecture characterized by to define the norms the agents should obey when they adopt
the implementation of agent’s beliefs, desires and intentions. a role. Figure 1 illustrates the graphical representation of
The AgentSpeak [13] is an abstract agent language founded organizational diagram elements.
on BDI model. Groups - A group is represented by means of a package
Jason [6] is a Java-based interpreter for an extended version with little men icon. It may contain several structural elements
of the AgentSpeak language. An AgentSpeak agent is defined (Roles) and other grouping elements (sub-groups). The root
by means of a set of plans that the agent is able to execute in group represents the entire organization.
certain situations. An AgentSpeak plan is defined as follows: Roles - A role is an UML class depicted as a little man. Its
properties are represented in the form of class attributes. Roles
+triggering − event : context < −body can be logically related to one another using associations. An
abstract role, instead, is identified using an italic font.
The Triggering Event describes the situations in which a Relationships - Model elements are related each others with
plan may be applicable for execution. The context can be used dependencies, associations and generalizations. A dependency
to specify the condition to make the plan applicable even if an is a generic relationship, indicating that an element depends in
event has triggered that plan. The body can be considered the some way on another. A generalization specifies a relationship
consequent of the event linked to the context. Within the body between roles in which specialized roles inherit features of the
commonly are defined the actions that agent must perform to general role. An association describes a link between elements
fulfill its own goals. of the Moise+ model. We used UML stereotypes in order to
attribute a semantic of the association with Moise+ domain-
C. J-Moise+ specific concepts.
J-Moise+ [5] is an implementation of the Moise+ organiza- In particular Moise+ organizational links, defining the way
tional model. J-Moise+ is based on Jason and consists of both in which social exchanges between agent roles occur, are
an OrgBox Api and a special agent called OrgManager. Agents represented by means of associations between roles labeled
use the OrgBox Api to access to the organizational layer. with an Authority, Acquaintance or Communication stereotype.
While the OrgManager stores the current state and maintains
the consistency of the Organizational Entity during its life-
cycle. J-Moise+ basically offers a set of actions to change the
state of the organization and produces some events related to
organizational changes to which the agent can react.

III. T HE P ROPOSED N OTATION
A detailed description of UML is out the scope of this paper,
we here define only the constructs used to model organizations
with Moise+. In the following subsections, we describe three
kinds of diagram applied to the classical example (”Writing
Paper”) reported in the Moise+ Tutorial [10]. Fig. 1. The Defined Notation Elements
Fig. 2. The Writing Paper Example - OD

Each propriety of a link can be expressed by UML association B. The Scheme Structural Diagram
constraints. The Moise+ Functional Specification deals with the con-
Moise+ compatibility links, instead, are defined by means cepts of agents’ missions and their global plans. Plan repre-
of associations between roles labeled with the Compatibility sents the set of goals to be pursued. Plans and missions com-
stereotype. Two roles connected by a bidirectional compatibil- pose (or are assembled into) the social scheme. We use two
ity link define the possibility of an agent to adopt both roles different views ( or models) for representing the elements the
at the same time. Each propriety of a link can be expressed functional specification is composed of: the Scheme Structural
by UML association constraints. Diagram (SSD) and the Scheme Functional Diagram (SFD).
Figure 2 shows the Organizational Diagram for the Writing The Scheme Structural Diagram allows to model the social
Paper organization. In this example, a set of agents aims to schemes of the organization through a UML class diagram.
write a paper. For this purpose, the Moise+ authors define an The elements of this diagram are:
organization with one group (wpgroup) and two roles (Writer Goal is represented by a class element reporting the name,
and Editor). These roles are an extension (represented by the stereotype and the attribute field; each of them corresponds
means of UML generalization in the OD) of the abstract to a specific feature of the Moise+ concept of goal: the class
role Author. An agent can play several roles only if they name addresses the goal id. The stereotype represents the
are compatible. As exemplified in figure 2, an agent playing two types of goal namely achievement and maintenance. The
the writer role can play the role editor at the same time and default type for every goal in Moise+ is achievement but in
vice-versa because they are linked by an UML compatibility the SSD the goal type has to be stated in any case. As regard
association. the attribute compartment, it basically contains the ttf attribute
In the Moise+ model, a role is usually linked by means of value prescribing the time requested for fulfilling the goal.
norms (Obligation or Permission) to one or more missions Mission is also represented through a class stereotyped as
defined in a particular scheme. mission. Here the attributes’ compartment contains values for
One of the Writer’s mission (see Figure 2) is mbib (i.e. the minimum and the maximum commitments to the mission.
getting references for the paper). The norm linking the mission The Social Scheme is modeled by means of a package
to the role is an Obligation, that is the agent playing the where classes (i.e. missions) are grouped in order to represent
Writer role must commit to this mission. This is shown in the the social organization of goals and missions. There can be
Organizational Diagram through the stereotype obligation. The more than one package in a single SSD thus representing the
Editor, instead, may commit to the mission mManager because existence of different schemes in the same organization. The
the link is a Permission norm. The association between roles is package’s name corresponds to the social scheme id.
stereotyped in order to represent organizational links such as As regard relationships among elements, in this diagram
Acquaintance, Compatibility, Communication and Authority. we only use two kinds of relationship: the aggregation and
the dependency; the latter is used for representing how two
different schemes depend on each other, the former is used for
relating missions and goals. With respect to Moise rationale,
goals are aggregated into missions that can be distributed/
committed to agents.

Fig. 3. The Writing Paper Example - SSD

Figure 3 shows a portion of the SSD for the write paper
example1 .
In the Scheme Structural Diagram, a Social Scheme is
Fig. 4. The Writing Paper Example - writePaperSch SFD
modeled by means of a package containing classes (i.e. mis-
sions and goals). Within a package the structural composition
of goals and missions is defined. For instance, the SSD for
done by agent to fulfill the goal. The elements of this diagrams
writing paper example is composed by two Social Schemes,
are:
writePaperSch and monitoringSch. The portion of writePaper-
Sch scheme reported in figure 3 shows how the mManager The Goal is then represented by an activity where the
mission is a composition of five goals: wp, wtitle, concl, wabs, name is the goal’s id and the stereotype represents the type
wsectitles that respectively aim to write the paper, the title, the of the goal (achievement or maintenance - see the previous
conclusion, the abstract and the title of each section. While the subsection) The Moise+ model allows to decompose goal in
illustrated portion of monitoringSch scheme shows ms mission sub-goals by means of a plan operator. There are three different
formed by only Sanctioning goal. In the SSD is also possible kinds of plan operator: sequence, parallelism and choice, the
to underline the dependences between different social schema. first means that a goal gi (having two sub-goals gi,i and gi,i+j
As 3 shown, the social scheme writePaperSch is related to ) can be achieved only if the close sequence of gi,i and
the monitoringSch scheme through a “monitoring” dependency gi,i+j ). All of them can be easily represented by means of
relationship. the UML activity diagram syntax, for instance the parallelism
is represented through the fork and the choice through the
C. The Scheme Functional Diagram decision diamond. Sequence is represented by a straight arrow
line.
The Scheme Functional Diagram represents the behavioural As said before, in this paper our concern is about the nota-
view of the Moise+ functional specification, it is realized by tion/models to be used for representing MAS organizations. If
means of an UML activity diagram and it aims at representing, we would use them during a design process phase we should
through a set of associated activities, how a goal can be consider that we can draw more than one SFD, one for each
decomposed in sub-goals. Each activity represents the work package (i.e. social scheme) of the SSD.
1 Because
Figure 4 and figure 5 show the Scheme Functional Diagrams
of space concerns only portions of dia-
grams are reported. Complete diagrams can be found in (SFD) built for the wp and monitoring goals of the Writing
http://www.pa.icar.cnr.it/cossentino/moisenotation/ Paper organization which are the root goals of writePaperSch
propose notations for agents, roles and the other elements of
their proposed metamodel.
Remaining in the context of AUML-related researches, it is
worth to remind the long work done by the FIPA Modeling
Technical Committee and its members at the beginning of
years 2000. In this context several proposals arose. Among
the others, Parunak and Odell presented in [15] some ideas
for the representation of social structures and relationships.
They introduced swimlanes in class diagrams in order to
partition the diagram in zones representing groups. Within
each organization the diagram may depict roles and the agents
playing them. Another proposed diagram was concerned with
Fig. 5. The Writing Paper Example - MonitorinSch SFD the description of the dynamic behavior of agents/roles in
terms of their interactions. Essentially it is an extension of the
UML 1.0 sequence diagram containing some notation elements
and monitoringSch (defined in the previous section) corre- that have been introduced in following versions of UML.
spondingly. The SFD of the writePaperSch (see figure 4) A more extended notation has been proposed by L. Padgham
explains how to achieve the root goal of the scheme. In detail, et al in [16]. This notation has been conceived with the aim
the fulfillment of the wp goal (i.e. write a paper) depends on of supporting most of the existing AOSE methodologies.
the achievement of the fdv (first draft version) and sv (submit An interesting point of this work is that the authors defined
version) goal. The sv goal is reachable only after that the fdv a notation leaving a large margin for the definition of the
is satisfied. In turn, fdv is achieved executing the atomic goals semantics that is behind that. In this way, the notation may
wtitle, wabs and wsectitles sequentially. be easily ported to support different approaches. More in
It is important to highlight there are three different types of details, it has been applied to O-MASE, PASSI, Prometheus
goal execution: sequential, parallel and choice. If two goals are and Tropos (partially). The notation includes graphical icons
related with a sequential relationship then the goal target can for representing almost all the elements of an agent-oriented
be reached only after that the source goal is reached. If two design, organizations included (agent, role, position, goal, . . . ).
goals are related with a parallel relationship then both goals From this point of view, the notation presented in [16] is
can be reached simultaneously. Finally, a choice relationship more complete than the notation we propose in this paper.
indicates that it is possible to choose the goal to achieve. However, the authors in [16] present several diagrams, none
Besides it is important to note that (see 4 and figure 5) the of them behavioral. This is a relevant difference with the work
root goal is represented with a box with the goal icon at the presented in this paper. In fact, our notation also includes the
top left corner instead of with an activity, this is due to the Scheme Functional diagram that is a behavioral representation
features of the tool we use for drawing activity diagrams. The of the system.
concept of goal does not depend on the graphical box they are INGENIAS [17][18] is a framework for developing MASs
represented but are related to the specific icon. offering to designers the possibility of following the workflow
of the methodology also with the aid of the tool (INGENIAS
IV. R ELATED W ORKS Development Kit IDK). The tool supports a specific notation
for representing the abstractions on which INGENIAS allows
A proposal for the introduction of groups in MAS modeling to develop MASs.
has been presented by J. Odell et al. in [14]. The proposed INGENIAS is suitable for modelling and developing MASs
metamodel is based on three main concepts: Agent, Agent with the following main abstractions: agent, task, role, organi-
Role (Classifier, Assignment) and Group. The peculiarity of zation, and goal. Modelling with INGENIAS implies basically
this approach is in the presence of the agentified group in using the Unified Software Development Process (USPD) [19];
opposition to the Non-agentified one. This does not represent each phase/iteration aims at developing different models or
an explicit attention for the presence of non-agent-oriented viewpoints on specific aspects of the MAS under development.
entities in the application. Conversely, non-agentified groups For the sake of the work proposed here we are interested in
are composed of agents just like the others, but they are not considering the Organizational Viewpoint.
addressable as an agent entity (i.e. the group does not exhibit The Organizational viewpoint describes the environment
the usual properties of an agent). Within a group, agents where agents live and interact each other by means of re-
interact according to the roles they play. sources and tasks in order to pursue goals. Modelling the
As regards the comparison of this work with the notation Organization is done by dividing the MAS into groups and
we presented in this paper, the authors of [14] present very workflows where all the involved entities are related by ag-
limited examples of notation. Mainly, a group is represented gregation and inheritance relationships; roughly speaking, in
in a form that resembles the UML class without the operation INGENIAS, groups give the mean to identify subsystems
and attribute compartments. Purposefully, the author avoid to interacting through workflows.
Each element of the Organization viewpoint has a precise V. D ISCUSSIONS AND C ONCLUSIONS
notational counterpart, for instance the goal is represented by In the field of agency, the complexity of current systems and
a circle and the group in a box with two kinds of head. This applications led to an increasing number of agents employed
allows to model how the organization is divided in groups in the multi agent system that must expose autonomous
(each group again can be decomposed in groups) made by and organizing capabilities also for substituting and making
agents that play roles. From a modelling point of view it is decisions on the behalf of user.
important to note that the goal is associated to the organization One important topic in these kind of systems is how to
and that in INGENIAS the concept of agent is central and is manage the agents by creating organizations in the same way
related to the concept of role whereas in MOISE+ the central the human, and more generally, the biological systems do.
element group and the role. This logical difference can be The design and the implementation of organization in MASs
found in the two notations and in the related diagrams we is related to this topic. Our work concerns the creation of a
can draw; anyway both of them allow representing the whole design process for developing MASs organized in hierarchical
portion of metamodel including organizational concept but structures, such as holons, that can be implemented with J-
INGENIAS does not provides means for representing norms. Moise+. In this paper we present the first step of this ongoing
Tropos [20] is an agent-oriented software engineering work: the UML-based notation to be used for representing
methodology mainly based on the notion of goal. organizational elements in the design process work products.
We created a notation enabling us to model organization
The Tropos methodology is articulated in four different
through three different artefacts where all the elements of
phases from the requirements analysis to the agent system
Moise+ organizational model are represented. One of the most
implementation. The requirements analysis covers two phases:
important results is that we eliminated the difficulty related to
the Early Requirements Analysis phase, concerning with the
the use of the predicative form for representing goal, norms,
studying of the problem, produces an organizational model and
etc. Moreover we obtained the capability of converting the
the Late Requirements Analysis phase where the system-to-be
work product, the diagram, in a xmi file and then through
is described. The agent system implementation is performed
an easy transformation in a xml file thus directly obtaining
through the Architectural Design phase, where the system
Moise+ code or better, if necessary, any other kind of code.
architecture is defined, and the Detailed Design phase where
all system components are specified. During the first two ACKNOWLEDGMENT
phases an actor and a goal diagram are produced. This work has been partially supported by the EU project
An Actor Diagram is a graphical representation of the appli- FP7-Humanobs and the IMPULSO project funded by the
cation domain stakeholders, their objectives and dependences. Italian Ministry for Economic Development.
A Goal Diagram is a refinement of the previous diagram un- Authors would like to thank Paolo Giorgini for his useful
derlining the goals of a single actor. These two diagrams show comments and suggestions.
essentially five concepts: Actors, Goals, Resources, Tasks and
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