Environmental Engineering Reference
In-Depth Information
The communications mechanism for components was based on a publish-
and-subscribe model, with a direct link between components when there was
a large amount of data to be transferred. Components communicated to each
other the types of data that they produced when queried. When one compo-
nent needed to be informed of new or changed data in another component, it
identified the data of interest and subscribed to it in the source component.
Data could be subscribed-to whenever they are changed or on an as-needed
basis. With this mechanism, a component could be added or removed without
having to modify the other components in the agent.
4.3.3 Dataflow Between Components
This section gives an example of how data flowed between components of the
architecture. In this example scenario, a spacecraft's battery is discharging.
Figure
4.6
shows a timeline and the flow of data between components. The
following is the scenario:
1.
The agent detects a low voltage by reading data from the battery via a
Perceptor. The Perceptor then passes the voltage value to the Modeler,
which has subscribed to the Perceptor to receive all percepts.
Planner
Scheduler Agenda
Executive
Perceptor
Effector
Comms.
Modeler Reasoner
new
voltage
value
changed -
send to
reasoner
set goal
to charge
battery,
send to
p/s
request
current
state
current
state
plan
verified
plan
plan step
request
next step
charge
battery
command
last step
executed
new
voltage
value
changed -
send to
reasoner
also
send to
executive
plan
finished
Fig. 4.6.
Scenario of data flowing between agent components
