The Moludar Agent Network they are an important conceptual extension to the model of Agents Networks [Guerrrero 2000]. A main contribution consists of the construction and simulation of hierarchical models in terms of RAs.
For a better understanding of
hierarchical models makes himself necessary the introduction of the notion
of heterogeneous system. A heterogeneous system is a constituted complex
entity of sub-system with different characteristics. Such systems is highly
competitive, so that the interactions among these sub-system can be extremely
complex and of quite different nature.
The recent progresses obtained in
efficiency and domain of the complexity during the modeling and project of
heterogeneous systems has been happening, basically, in function of the
introduction of new languages and methodologies that bring additional levels of
abstraction. Everything this enables the planners to treat the complexity
continually growing in adapted detail levels. Heterogeneous systems frequently
show a complex behavior that cannot be completely or easily described in a
simple formalism. Thus, it is desirable the existence of another appropriate
formalisms to these types of problems. The simulation of complex systems can be
favored by a representation in multiple abstraction levels.
Hierarchy
The notion of the hierarchy is about the construction of structures capable to attribute resolution levels and/or abstraction to the model of a system.
Hierarchies in Agents Networks
In the context of RAs, constituted of
places, arches and objects, two possibilities of introduction of mechanisms of
hierarchical structuring exist:
I) replacement of
a sub-network for a super-place. The semantics of a sub-network is in certain
way adapted to the semantics from a place. The composition is made by
the connection of private gates of input and output, being used the notion of
coalition of places. The components of the hierarchy have a strong joining,
because the organization of the connections is defined directly in the
configuration of places and arches.
II) replacement of a sub-network for a super-object. The semantics of a sub-network is adapted to the semantics of an object. It can be said that in this case the joining is that in this case the joining is weak, because the connection of the gates follows the same begin of the sensor and atuadores in a formal agent.
The structure of a Modular Agent Network (RAM) is constituted by a grouping of instances of you make up of sub-network connected to each other. Under this point of view, one makes up it can be faced with an abstract it data type. One makes up it is a generic specification of a collection of places, arches, sub-network interfaces and super-place that it can be instanciada.
The places and arches in a RAM follow the original definition [Guerrero 2000]. Two others elements are added: super-places and interfaces (of sub-network).
Super-place: is an entity topological that represents an entire sub-network.
Interface: it introduces a similar behavior that associated to a conventional place, being used for communication with you make up pages-father. This communication is based on a mechanism called coalition of places, typically employee in Hierarquical Coloured Petri Net (HCPNs) to implement the composition of hierarchical structures. To say that two or more places present a coalition relationship it is equal to the statement that they are in fact the same place - all the operations applied one of them are reflected in the other ones, as well as the properties (objects located in its interior, public and private gates).
Three concepts many important exist in the construction of a Modular Network:
Page: is a generic specification that it indicates a certain configuration of places, arches, interfaces and super-places. A page can include (or in a certain way to inherit) the specification of another page for the inclusion of a super-place of this other page.
Super-Place: it represents the incorporation of a page to the definition of another. Thus, a super-place, is a reference to a page, in a similar format to a conventional place. It is possible to compare a page to a class in languages guided to objects.
Instance of Page: So that it is possible similar a to Modulate Network (formed by a collection of interrelated pages) it is necessary to create an instanciação tree, that describes a collection of instances of pages where each one of these instances receives an only identify. This identification is justified because a same page can be inside instanciada multiple times of a same net. A convention is adopted in which each page instance receives an object identifier (oid). As basic requirement, is considered that the system that implements the simulation process is capable to attribute an oid it is only OID to all the instances of pages in the moment of its creation. (Figure 4.1 Tese de Antonio)
Figure 4.1 Entities topologicals possible in a page.
A page can include super-places of another pages, forming a hierarchy of pages. The only restriction that this hierarchy should satisfy is that the graph formed, in which the knots are represented by the pages and the arches by the inclusion restrictions (created by the super-places), they should form a reticulado obligatorily.
For the representation of hierarchies of pages a format is used similar to the adopted in the diagrams of classes in UML (Unified Modeling Language). This format is denominated diagrams of pages tends its components illustrated in it Figure 4.2...tese de Antonio
Figure 4.2 Notação maid for diagrams of pages.