Logical deductive system
In domain theory, a branch of mathematics and computer science, a Scott information system is a primitive kind of logical deductive system often used as an alternative way of presenting Scott domains.
A Scott information system, A, is an ordered triple



satisfying





Here
means
The return value of a partial recursive function, which either returns a natural number or goes into an infinite recursion, can be expressed as a simple Scott information system as follows:



That is, the result can either be a natural number, represented by the singleton set
, or "infinite recursion," represented by
.
Of course, the same construction can be carried out with any other set instead of
.
Propositional calculus
[edit]
The propositional calculus gives us a very simple Scott information system as follows:



Let D be a Scott domain. Then we may define an information system as follows
the set of compact elements of 


Let
be the mapping that takes us from a Scott domain, D, to the information system defined above.
Information systems and Scott domains
[edit]
Given an information system,
, we can build a Scott domain as follows.
- Definition:
is a point if and only if


Let
denote the set of points of A with the subset ordering.
will be a countably based Scott domain when T is countable. In general, for any Scott domain D and information system A


where the second congruence is given by approximable mappings.
- Glynn Winskel: "The Formal Semantics of Programming Languages: An Introduction", MIT Press, 1993 (chapter 12)