database. Each node represents a table. Tables that are part of the
``root set'' are shown with double borders. Each edge leads from the
table that contains it and points to the table that its value
-represents. Edges are labeled with their column names. Thick lines
+represents. Edges are labeled with their column names, followed by a
+constraint on the number of allowed values: \\fB?\\fR for zero or one,
+\\fB*\\fR for zero or more, \\fB+\\fR for one or more. Thick lines
represent strong references; thin lines represent weak references.
.RS -1in
"""