Systems, Man & Cybernetics - July 2015 - 29

E-CARGO model are much easier to
reuse than the concepts because of
formalizations. In addition, to make
this article more readable, detailed
formalizations are omitted. Readers
interested in the formal definitions
of the E-CARGO components may
refer to [84].

Start

Yes!

Role Negotiation

Abort

No!

Is There an
Agreement?
Yes!

No!
First-Class Components of the
Is It
Negotiable?
E-CARGO Model
Agent Evaluation
Yes!
From the viewpoint that everything
in the world is an object, each of
which has a class, we have the defiRole Assignment
nitions for classes and objects. A
class is an abstraction and template
of entities that have similar propIs Reevaluation
Role Transfer
Role Playing
No!
No!
Needed?
erties and features. An object is an
expression of an entity that is not a
Yes!
role-player in RBC and E-CARGO.
Can Roles
Is There a
A role is an entity that represents
Yes!
Transfer?
Problem?
a combination of responsibilities,
rights, and objects that can be conNo!
centrated on or ignored based on
concrete applications. Note that the
No!
Is the
current agent set A c and the potenCollaboration
tial agent set A p in the definition of
Done?
a role are empty before a group is
formed, i.e., a role can be specified
Yes!
before agents are specified. On the
End
other hand, the E-CARGO model
does not restrict the details of their
components, including roles. A role Figure 1. The life cycle of RBC.
can be defined in different ways in
modeling specific problems.
improve the performance of a group, including agent evaluAn agent is a role-player. In the definition of an
ation and role assignment.
agent, all of the current and potential roles of agent
In general, E-CARGO clearly differentiates among its coma (i.e., a.R p , " a.rc ,) for m its repositor y role set.
ponents. Objects are not agents and do not play roles. Agents,
If a.rc is empty, then a is currently free. The term
as role-players, deal with the messages dispatched by their
agent can be any entity described by the definition,
roles and access objects with the rights regulated by their
such as a human being, software agent, machine, or
roles. Roles are message exchangers and dispatchers. Envicommodity. It does not have to carry the meaning of
ronments are specified by roles and objects. A group is comthe term agent in MASs [10], [11], [28] if researchers
posed of dynamic agents in an environment by playing roles.
only concentrate on the relationships between roles
and agents. In addition, this definition leaves space to
express the traditional agent concept. In E-CARGO,
Supplemental Components of the E-CARGO Model
we could conduct "divide-and-conquer" and "optimiA message is a way to facilitate the interactions among
zations" to deal with collaboration problems among
the components of the E-CARGO model. In RBC, we
agents. Note that the definitions are developed conemphasize that messages are sent to roles. Messages
tinuously from their original forms [58]-[87] to accomare exchanged among roles. A role is also a message
modate changing requirements.
dispatcher to the agents that are playing this role.
An environment is a plan, proposal, or blueprint to
Therefore, in E-CARGO, objects are passive entities
establish a team. A group is a team of agents to be estabthat are accessed by agents through roles. Objects canlished to fit an environment. From the definition of a
not process messages. Role-players, i.e., agents, are the
group, we emphasize the role assignment to agents. From
only components to process messages. This idea clarithis point of view, many challenges can be discovered to
fies the differences among agents, roles, and objects.

Ju ly 2015

IEEE Systems, Man, & Cybernetics Magazine

Table of Contents for the Digital Edition of Systems, Man & Cybernetics - July 2015