typedef struct a_word_source {
   a_sql_uint32 ( SQL_CALLBACK *begin_document )(
                                a_word_source *This
                                , a_sql_uint32 has_prefix );
   a_sql_uint32 ( SQL_CALLBACK *get_words )(
                                a_word_source *This
                                , a_term** words
                                ,a_sql_uint32 *num_words );
   a_sql_uint32 ( SQL_CALLBACK *end_document )( 
                                a_word_source *This );
   a_sql_uint32 ( SQL_CALLBACK *fini_all )( 
                                a_word_source *This );

   a_server_context    *_context;

   // Only one of the following pointers can be valid 
   // in any implementation.
   // For example: if the producer for this module is
   // a a_text_source, then only my_text_producer will 
   // be a valid pointer whereas my_word_producer 
   // should be assigned a NULL
   a_text_source       *_my_text_producer;
   a_word_source       *_my_word_producer;

   // Following members have been reserved for 
   // future use ONLY
   a_text_source       *_my_text_consumer;
   a_word_source       *_my_word_consumer;
} a_word_source;