An index can be typeset relating the names defined in a specification to the page numbers on which their definitions are typeset. All names defined in the same source file, up to this point in the specification, are listed in the index. Each name is followed by a key-letter indicating how it was defined.
The troff mark-up of an index directive is as follows, on a line by itself.
.ZN
The LATEX mark-up of an index directive is as follows, on a line by itself.
\%\%index
There is a separate directive that typesets a key to the key-letters, which looks similar to this.
c = element or injection s = schema definition g = given set t = free type k = knob v = variable
The troff mark-up of the key directive is as follows, on a line by itself.
.ZZ
The LATEX mark-up of the key directive is as follows, on a line by itself.
\ZZ