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rather than what a program has the capacity to do. This defi nition lands us
back in the territory of interaction with human and computer-based agents.
It also contains a word we haven't used yet: “program.”
A program is a set of instructions that defi nes the potential actions that
make up a human-computer activity and their representations. These ac-
tions and representations may change as the result of ongoing action (for
instance, as the result of capturing or inferring people's preferences). A
program also defi nes the environment for action and the other objects that
inhabit that environment, including their representations and capabilities.
Actually, the elements of action and environment and their representations
are always the result of more than one program—in most computational
devices, many aspects of the “interface” are embedded in the operating sys-
tem and layers of intermediate software libraries. Of course, the potential
of a program is also shaped by the language in which and the hardware for
which it is written—what kind of computation it can perform, for instance,
the qualities of its display, and its interface affordances.
In theatrical terms, a program (or a cluster of interacting programs) is
analogous to a script, including its stage directions. A script is constrained
by the physical realities of the kind of theatre in which it is to be performed
and the capabilities of the stage machinery and actors. Program code is
equivalent to the
words
of a script (including the theatre's own brand of
jargon; e.g., “move stage left” or “counter-cross”). In his investigations of
artifi cial intelligence, Professor Julian Hilton adds another dimension to
this analogy:
The text [of a play] therefore, is a combination of explicit and implicit
notational systems which have as their initial purpose the enablement
of an event in which performers and audience can share as partners.
While obviously the notion of a computer was alien to Shakespeare,
that of his theatre as a complex space-time machine was certainly
not. . . . (Hilton 1991)
Functionality is equivalent to the script parsed, not by words but by
ac-
tions
. An apparent difference between programs and theatrical scripts is
that programs are not intrinsically linear in form, while scripts generally
are. At the highest level, this nonlinearity means that programs can cause
different things to happen depending upon the actions of their interactors;
that is, “authorship” is collaborative in real time (this aspect will be further
