rmat "%{+family,familylang{sub-expr}}" will expand "sub-expr"
with a sub-pattern consisting only the family and family lang elements of
<TT
CLASS="PARAMETER"
><I
>pattern</I
></TT
>.&#13;</P
><P
>&#13;A <I
CLASS="FIRSTTERM"
>conditional</I
> tag
is one starting with the character "?" followed by a
comma-separated list of element conditions, followed by two sub-expression
enclosed in curly braces.  An element condition can be an element name,
in which case it tests whether the element is defined in pattern, 