The left-hand side of a production contains a nonterminal symbol and, for the adaptive top-down parser atd-parser, optionally, a spur update mode specifier #su… (see Switching Spur Update Mode).
The nonterminal symbol does name the production and must not occur at left-hand sides of copying assignments and other productions.
Note: bottom-up template grammars support including in production left-hand sides a marker
#l-…indicating a nonterminal symbol at the left-hand side of a production of a source PCFG; see Marking a Left-Hand Side, for more information about this marker.
On calling the adaptive bottom-up parser abu-parser without passing the option --viterbi or on calling the adaptive top-down parser atd-parser, a nonterminal symbol at a production left-hand side must be a simple nonterminal symbol.
Example
AB: ... ;
On calling abu-parser with passing the option --viterbi, if a nonterminal symbol at a production left-hand side is a start nonterminal symbol, it must be compound one, otherwise it can be simple or compound one.
Example
START/1: ... ;
A spur update mode specifier #su… at the left-hand side of a production sets its initial spur update mode to “enabled” or “disabled”.
As default initial spur update mode is “enabled”, it only makes sense to set initial spur update mode to “disabled” by the spur update mode specifier #su0, if necessary.
Example
AB #su0: ... ;