.TH tabletofact "" "" "/rdb Command"
.PC "Converts a table to PROLOG fact-file format"
\fBtabletofact \fItable ... \fB> \fIprologfactfile\fR
.PP
.II "table^convert to PROLOG facts"
.II "convert table to PROLOG facts"
.II "PROLOG^convert table to facts"
The command
.B tabletofact
converts each
.I table
into a file of facts in predicate calculus functor form,
which can be input to a PROLOG interpreter.
.SH Facts
PROLOG
facts are in the form
.IR relationship(subject,object) .
For example, the fact
.DM
	parent(sally,fred)
.DE
.PP
means that ``sally is the parent of fred''.
.PP
PROLOG is a programming language whose name is a contraction of the phrase
.IR "programming in logic" .
Its input consists of 
.IR facts ,
.IR rules ,
and
.IR questions .
If you build a data base of facts and rules,
you can ask questions and get answers.
If a question you ask does not have a
corresponding fact in the data base,
PROLOG looks through its rule file to see if other facts might
logically deduce the fact requested.
.SH Example
Suppose we have these simple table
.B parent
.DM
Parent  Child
------- -------
Sally   Fred
Mike    Fred
Fred    Jane
.DE
.PP
the simple table
.B female
.DM
Name
----
Jane
Sally
.DE
.PP
and the simple table
.BR male :
.DM
Name
----
Fred
Mike
.DE
.PP
The command
.DM
	tabletofact parent female male > fact
.DE
.PP
produces the following facts:
.DM
parent(Sally,Fred).
parent(Mike,Fred).
parent(Fred,Jane).
female(Jane).
female(Sally).
male(Fred).
male(Mike).
.DE
.PP
As you can see,
the relationship is set by the name of the table, and the subject and
object (if any) are set by the data in each row.
.PP
PROLOG
can now use its command
.B consult
to read this file.
If PROLOG
had rules about father, mother, grandparent, and so on,
then it could answer questions like:
.B mother(sally,fred)?
That fact is not in the data base, but can be deduced from rules like:
.DM
	mother(X,Y) if parent(X,Y) and female(X)
.DE
.PP
.SH "See Also"
.B
tabletorule
.R
.SH Notes
.II COHware
If you wish to experiment with PROLOG,
volume 2 of
.B COHware
includes the source code for a PROLOG interpreter.