INTELLIGENT CONTROL OF MATERIAL HANDLING SYSTEMS - Environmentally Conscious Materials Handling - page 93

Figure 3.18 EBS elements, here storing a line of empty totes

and complicate the simple routing principles. Instead, agents can be assisted by
a mediator agent that collects aggregated information for the entire system. In
the initialization process, the RouteAgent generates all possible routes in the
system by building up a graph for the BHS with nodes corresponding to the
element agents. During the operation, it constantly monitors traffic on all edges
of the graph and update the weights in the graph, so dynamic shortest paths
can be calculated using classic Dijkstra for dynamic shortest path calculations
(Dijkstra 1959).
Following the FIPA query-ref communication act, element agents can request
routes to a given destination packed in a referential expression of the query mes-
sage. The referential expression is composed using an ontology that has been
defined for the BHS domain, which extends and follows the structure of the
FIPA-SL. The RouteAgent understand two concepts of the ontology, RouteBe-
tween and LineBetween :

1. RouteBetween is the concept used, when agents are interested in full
or parts of a route, but only with a granularity of finding other ele-
ment agents along the path — only information on nodes of the graph are
returned.
2. LineBetween is the fine-grained concept providing all details about a con-
veyor line of connected elements in the BHS — information about edges
between two given connected nodes.