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2 The Hierarchical Paradigm

Figure 2.1 Shakey, the first AI robot. It was built by SRI for DARPA 1967–70. (Pho-
tograph courtesy of SRI.)

a path. Strips will serve to motivate the reader as to the computer challenges
inherent in even as simple a task as walking across a room. However, Strips
is not an architecture, per se, just an interesting technique which emerged
from trying to build an architecture. Two representative architectures are
presented, NHC and RCS, that serve as examples of robot architectures pop-
ular at the time. The chapter concludes with programming considerations.

2.2 Attributes of the Hierarchical Paradigm

As noted in Part I, a robotic paradigm is defined by the relationship between
the three primitives (SENSE, PLAN, ACT) and by the way sensory data is
processed and distributed through the system.
The Hierarchical Paradigm is sequential and orderly, as shown in Figs. 2.2
and 2.3. First the robot senses the world and constructs a global world map.
Then “eyes” closed, the robot plans all the directives needed to reach the