- * <PRE>
- query ::= top-set query-struct.
- top-set ::= [ '@attrset' string ]
- query-struct ::= attr-spec | simple | complex | '@term' term-type
- attr-spec ::= '@attr' [ string ] string query-struct
- complex ::= operator query-struct query-struct.
- operator ::= '@and' | '@or' | '@not' | '@prox' proximity.
- simple ::= result-set | term.
- result-set ::= '@set' string.
- term ::= string.
- proximity ::= exclusion distance ordered relation which-code unit-code.
- exclusion ::= '1' | '0' | 'void'.
- distance ::= integer.
- ordered ::= '1' | '0'.
- relation ::= integer.
- which-code ::= 'known' | 'private' | integer.
- unit-code ::= integer.
- term-type ::= 'general' | 'numeric' | 'string' | 'oid' | 'datetime' | 'null'.
- * </PRE>