Information Technology Reference
In-Depth Information
Fig. 9.1
The problem with
dual semantics
Problem Domain
Program
Computer States (bits)
Fig. 9.2
The only rational
interpretation of a computer
program
Program
Computer States (bits)
-
T3.11
, We use the perceptible sign of a proposition (spoken or written, etc.)
as a projection of a possible situation. The method of projection is to think of
the sense of the proposition.
•
T3.32
, A sign is what can be perceived of a symbol.
•
T4.01
, A proposition is a picture of reality. A proposition is a model of reality as
we imagine it.
•
T4.021
, A proposition is a picture of reality: for if I understand a proposition, I
know the situation that it represents. And I understand the proposition without
having had its sense explained to me.
and a proposition can have one and only one complete analysis:
•
T3.25
, A proposition has one and only one complete analysis.
Such an analysis is dependent upon only the essential features of the proposition (the
program) that link it to the referent objects (which is the bit in our case).
A computer program, as we have already seen, has such an analysis with respect to
the computational engine (Fig.
9.2
), so the 'alternative' interpretation of a program,
the problem domain, depends upon its accidental features.
•
T3.34,
A proposition possesses essential and accidental features. Accidental fea-
tures are those that result from the particular way in which the propositional sign
is produced. Essential features are those without which the proposition could not
express its sense.
This develops a peculiar tension in program design that is hard to keep stable, partic-
ularly with respect to the informal, and often undefined, mechanism which links the
program names with the user's domain. Further, the 'objects' that are usually chosen
to be referenced in the informal analysis of the problem domain do not normally
have all the features required of Wittgenstein's objects. For example, they usually
cannot be unambiguously defined. This is because no set of rules can be formulated
to identify completely most objects that exist in the world as recognisable entities.
Simple distinctions such as the computer bit are possibilities provided there is some
well-defined formal definition of what is meant by a bit. However, computer engi-
neers can find examples of bits that are indeterminate, and it is for this reason that
sum check bits accompany every computer word. These check bits provide additional
information so that bits that are ambiguous can be detected and made distinct.
