ENABLE Reference Manual

ENABLE ATTRIBUTES
TREE Attribute
The order that you define with a LINK OPTIONAL establishes a
dependency between the records associated with both boxes. When
you define a LINK OPTIONAL, you indicate that the application is
to use the join field value of a record from one box to read or
insert a record in the other box. Thus, the records in the
second box can be said to depend on a matching record in the
first box for access by the application. Records match if their
join field values are the same.
Since the dependency established for a LINK OPTIONAL is similar
to the dependency condition that exists between a parent and a
child, one of the boxes connected by a LINK OPTIONAL is called a
parent box and the other is called a child box. In this context,
the application can read or insert a record for a child box only
if it has already read or inserted a matching record for the
parent box.
Figure 4-5 illustrates an application that uses "employee-box" as
the parent box and "depend-box" as the child box. (Figure 4-4
shows part of the records associated with these boxes.)
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