Rdb: Ruby-Nachbau der MWC /rdb-Werkzeuge

man/tabletofact.man

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+.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.