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is determined by the type of existing relation between roles, which establishes their
hierarchy. However, VOF defines this hierarchy using the
RoleHier
relation.
In MOISE
Inst
, the structural levels of the organization are split into: (i)
individual
level
, built by organizational roles, and presents hierarchy relations between roles (sim-
ilar to our
RoleHier
relation); (ii)
social level
, which is built from link relationships
between roles, classified as
acq
(
acquaintance
), i.e. having a representation of other
agents,
com
(similar to our
in f
relation), in which agents are able to communicate be-
tween them, and
aut
expressing authority over other agents, thus combining
col
and
sup
relations from VOF; and (iii)
collective level
, which defines
groups
of agents, establish-
ing the
compatibility
between roles and their
cardinalities
. VOF adds the
comp
relation,
in order to express whether an agent can take a given role if he is taking another one.
LAO models the topology of the system by means of dependency chains between
agents. The topology can be a
hierarchy
, if there is a chain of command, or a
network
,
if every agent is responsible for an organizational goal and has a delegation relation-
ship to another agent. VOF models the topology of the system using
Contains
relations
between OUs. These relations allow defining three types of organizations:
hierarchy
,
similar to the structure defined by LAO;
team
, when all agents collaborate with each
other; and
plain
, which assumes information relationships between roles.
Regarding the Functional Dimension, although PopOrg and POMF model concepts
that are similar to services (by means of exchange processes or workflows, respec-
tively), they are better described in VOF. PopOrg focuses on the actions developed by
the process and the agents that are carrying them out, while POMF is focused on de-
scribing the tasks that compose a given workflow. VOF goes beyond, (as it follows a
Service Oriented Approach) and formalizes a service by means of the roles that it can
provide and consume, the goals that can be achieved with this service, the invoke re-
lationships between services, and the tasks that compose each service (as well as the
goals that these tasks help to reach).
TheenvironmentusedinVOFisbasedonthe Agents & Artifacts conceptual frame-
work, which was included in the SODA metamodel [19].
VOF model norms in a very similar way to the proposal of MOISE
Inst
, although they
use different languages to describe them. VOF is able to relate a norm to a set of OUs,
using the
Norms
relation from
DimRelations
, limiting its effect only to this set.
The Organizational Entity from VOF can be also compared with other proposals. For
example, a specified group is defined in MOISE
Inst
as a 'group specification', while
VOF defines it as an Organizational Unit. On the other hand, a group instantiation is
named 'group' in both MOISE
Inst
and VOF. In addition, the
OE
from VOF defines the
set of norms and services that are currently active in the organization.
Finally, VOF clearly divides the elements that specify the system (i.e. elements that
will produce a structural change if they are modified) and the more dynamic elements
of the MAS, represented in the
OE
. Our specification gives agents the possibility to
belong to a specific group and provide or use a service.
6
Conclusions and Future Work
This work presented a formal specification for Virtual Organizations, named VOF (
Vir-
tual Organization Formalization
), which is composed of: (i) the Organizational
