Page 174 - Introduction to AI Robotics

5.2 Behaviors as Objects in OOP
Schema Behavior 157
coordinated control program coordinated control program

* * *
Perceptual Motor Behavior Perceptual Motor Behavior
Schema Schema Schema Schema
a. b.
Figure 5.1 Classes: a.) schema and b.) behavior.

5.2 Behaviors as Objects in OOP

Although Object-Oriented Programming (OOP) had not become popular dur-
ing the time that the Reactive Paradigm was developed, it is useful to cast
behaviors in OOP terms. Schema theory is well suited for transferring theo-
retical concepts to OOP. Furthermore, schema theory will be used as a bridge
between concepts in biological intelligence and robotics, enabling a practi-
cal implementation of reactivity exploiting innate releasing mechanisms and
affordances.
Recall from software engineering that an object consists of data and meth-
ods, also called attributes and operations. As noted in Ch. 3, schemas con-
tain specific knowledge and local data structures and other schemas. Fig. 5.1
6
shows how a schema might be defined. Following Arbib, aschema as a
programming object will be a class. The class will have an optional method
COORDINATED called a coordinated control program. The coordinated control program is a
CONTROL PROGRAM function that coordinates any methods or schemas in the derived class.
Three classes are derived from the Schema Class: Behavior, Motor Schema,
and Perceptual Schema. Behaviors are composed of at least one Perceptual
Schema and one Motor Schema; these schemas act as the methods for the
Behavior class. A Perceptual Schema has at least one method; that method
PERCEPT takes sensor input and transforms it into a data structure called a percept.A
Motor Schema has at least one method which transforms the percept into a
vector or other form of representing an action. Since schemas are indepen-
dent, the Behavior object acts as a place holder or local storage area for the
percept. The Perceptual Schema is linked to the sensor(s), while the Mo-
tor Schema is linked to the robot’s actuators. The sensors and actuators can
be represented by their own software classes if needed; this is useful when
working with software drivers for the hardware.