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We require that grammatical analysis finds all maximal projections anywhere in the input word-graph. This implies that the top category of the grammar should be defined in such a way that it derives each of these maximal projections. For this reason, the grammar contains the declaration:
\begin{displaymath}\small\begin{minipage}[t]{.9\textwidth}\begin{verbatim}top_category(X) :- X => start.\end{verbatim}\end{minipage}\end{displaymath} (27)

Furthermore, there are unary rules rewriting this start category into each of the relevant maximal projections. One such rule is:

...t, Np => np,
Start:sem <=> Np:sem.\end{verbatim}\end{minipage}\end{displaymath} (28)

Similar rules are defined for pp, sbar, root, advp, etc.