The object of having a mapping module is to dispense with the need for the manual design of DEDS automaton for various platform tasks. In particular, we would like to have an off line module which is to be supplied with some symbolic description of the task under observation and whose output would be the code for a DEDS automata that is to be executed as the observer agent. The problem reduces to figuring out what is an appropriate form for the task description. The error state paradigm motivated regarding this problem as the inverse problem of determining acceptable languages for a specific DEDS observer automaton. In particular, we suggest a skeleton for the mapping module that transform a collection of input strings into an automaton model.
The idea is to supply the mapping module with a collection of strings that represents possible state transition sequences. The input highly depends on the task under observation, what is considered as relevant states and how coarse the automaton should be. The sequences are input by an operator. It should be obvious that the ``Garbage-in-garbage-out'' principle holds for the construction process; in particular, if the set of input strings is not representative of all possible scene evolutions, then the automaton would be a faulty one. The experience and knowledge that the operator have would influence the outcome of the resulting model. However, it should be noticed that the level of experience needed for providing these sets of strings is much lower than the level of experience needed for a designer to actually construct a DEDS automaton manually. The description of the events that cause transitions between different symbols in the set of strings should be supplied to the module in the form of a list.
As an illustrative example, suppose that the task under consideration
is simple grasping of one object and that all we care to know is three
configurations; whether the hand is alone in the scene, whether there
is an object in addition to the hand and whether enclosure has
occurred. If we represent the configurations by three states ,
and
, then the operator would have to supply the mapping
module with a list of strings in a language, whose alphabet consists of
those three symbols, and those strings should span the entire language,
so that the resulting automaton would accept all possible configuration
sequences. The mapping from a set of strings in a regular language into
a minimal equivalent automaton is a solved problem in automata theory.
One possible language to describe this simple automaton is :
and a corresponding DEDS automaton is shown in
Figure 2.
The best-case scenario would have been for the operator to supply
exactly the language to the mapping module with the appropriate
event definitions. However, it could be the case that the set of
strings that the operator supplies do not represent the task language
correctly, and in that case some learning techniques would have to be
implemented which, in effect, augment the input set of strings into a
language that satisfies some pre-determined criteria. For example,
is substituted for any string of
's having a length greater
than
, and so on. In that case the resulting automaton would be
correct up to a certain degree, depending on the operator's experience
and the correctness of the learning strategy.