[antlr-interest] Lexer Rules How to

[maxgbr at hotmail.it]

Hi, i'm a newbie of Antrl and i have some trouble with the lexer rule.
I want to create a very semplified Oracle syntax parser to get only few informations out of the sql's and i run into this issue [NoViableAltException]in ANTRLWorks when i try to debug this rules:

grant_statement
    :    'GRANT'
    (    grant_system_privilege
    |    grant_object_privilege
    ) 
    ;

grant_object_privilege
    :    privilege[false] (COMMA privilege[false])* 'ON' on_object_clause    
        grantee_clause ('WITH' 'HIERARCHY' 'OPTION')? ('WITH' 'GRANT' 'OPTION')?    
    ;
    
privilege[boolean isSystemPriv]
    :    {isSystemPriv }? priv_sys
    |    {!isSystemPriv}? priv_obj
    ;

priv_obj
    :    IDENTIFIER        // SELECT
    |    IDENTIFIER IDENTIFIER    // CREATE SESSION
    |    'ALL' 'PRIVILEGES'?
        LPAREN IDENTIFIER (COMMA IDENTIFIER)* RPAREN
    ;

priv_sys    
    :    IDENTIFIER+
    |    'ALL' 'PRIVILEGES'
    ;

grant_system_privilege
    :    privilege[true] (COMMA privilege[true])*
        grantee_clause ('IDENTIFIED' 'BY' .+)? ('WITH' 'ADMIN' 'OPTION')?
    ;

grantee_clause
    :    'TO' (IDENTIFIER
    |    'PUBLIC'
    )    (COMMA (IDENTIFIER | 'PUBLIC'))*
    ;

system_privilege
    :    IDENTIFIER
    ;

IDENTIFIER
    :    LETTER (LETTER | DIGIT | '_' )*
    ;    

with this sql         -> GRANT UPDATE , SELECT ON emp_view TO PUBLIC;  <- throw NoViableAltException 
but with this sql   -> GRANT update, SELECTON emp_view TO PUBLIC; <- all goes fine.

i have a token definition for UPDATE like

tokens {
   UPDATE = 'UPDATE';
}

but the update token is used in another rule [update_statement], not in this one.

I cannot figure out why the UPDATE token make my grant priv_obj rule to throw that exception.
How can i solve this problem??

Sorry for my bad english..

Thanks Max