CREATE [OR REPLACE] INDEXTYPE [schema .] indextype FOR 
[schema .] operator ( paramater_type [, paramater_type]... ) 
[, [schema .] operator ( paramater_type [, paramater_type]... )]...
USING [schema .] implementation_type;

For information on the symbols and conventions of Backus-Naur Form (BNF) syntax, see Appendix A.