We are interested in social virtual worlds which emulate activities in a real institution. For
the specification of the institutional rules, we use electronic institutions (Esteva, 2003), a
well-known MAS methodology. The institutional rules establish the valid interactions
agents may have and the consequences of those interactions. Specifically, institution
designers should define the following components (the formalization of these components
can be found in (Arcos et al. 2005)):
16 Web Intelligence and Intelligent Agents
Dialogical framework. It establishes the common ontology and communication
language to allow agents to exchange knowledge and understand each other.
Social structure. It establishes the roles that the agents may play within the
institution and the relationships among them. Each role defines a pattern of
behaviour within the institution.
Scenes. Each scene defines an interaction protocol among a set of roles. The
protocol, specified by a finite state machine (FSM), establishes the valid interactions
that agents may have. The nodes of the FSM represent the different conversation
states, while the arcs are labelled with messages of the communication language or
timeouts. A scene specification also defines at which states agents, depending on
their role, can join or leave.
Performative structure. It defines the role flow policy among scenes, that is, how
agents depending on their role can move among the different scenes. The
performative structure is specified as a graph. Graph's nodes are scenes and
transitions, and arcs are labelled with the roles that can progress through them.
Transitions are a kind of routers that permit to express synchronisation,
parallelisation and choice points for agents moving between scenes.
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Norms. They capture the consequences of agents' actions within the institution.
Such consequences are modeled as commitments (obligations) that agents acquire
as the result of their actions. It is worth mentioning that the specification also
includes the definition of the information model that the institution uses to keep
the state of participants and activities going on at run time. For instance, an auction
house may keep for each buyer her current credit and the list of purchased goods.
This is specified as a list of attributes (or properties) associated to some of the
previous elements. The specification of the institutional rules is supported by
ISLANDER, the electronic institutions specification tool (Arcos et al. 2005).
At design time, the specification focusses on macro-level (rules) aspects of agents not in their
micro-level (players) aspects. No assumptions are made at specification time about the
internal architecture of participating agents. Hence, participants can be human and software
agents. Electronic institutions infrastructure at run-time is named AMELI which is in charge
of guaranteeing the participants do not violate the institutional rules established at design
time.