Enter the define command
<"links"
define!links@"links"
links@"links"
to begin entry of link definitions.
All entries until the next "define" subcommand
are link definitions.
Each has the following syntax.
«link name> "from" <att1> "in" <rel1> "to" <att2> "in" <rel2>
where the value of column <att1> in table <rel1>
will be used to find a unique row of table <rel2>,
where <att2> = <att1>.
Links are used by the "select" command.