Thanks, that helps a lot. However, it is incomplete (a.k.a. 'broken'). I've got basic SELECT, FROM, and JOIN clauses parsing now, but I'm getting a little bogged down on the logical expression for the WHERE clause. Does HQL support *all* of the logical expression variants that SQL does?

Essentially, yes.

A few questions, if I may:

1) The BNF indicates that the 'HAVING' clause can exist without being preceeded by 'GROUP BY'. Does this make sense? Other SQL BNF's make the 'HAVING' clause an optional element of 'GROUP BY'.

2) The following rules are not referenced in the BNF:

collection: ( OPEN query CLOSE ) | ( 'elements'|'indices' OPEN path CLOSE );

quantifiedExpression: 'exists' | ( expression 'in' ) | ( expression OP 'any' | 'some' ) collection;

compoundPath: path ( OPEN_BRACKET expression CLOSE_BRACKET ( '.' path )? )*;

What are they for, and where should they be used?

3) COUNT() has it's own special cases (e.g. '*'), but should this really be handled by the grammar?

1) No, you can't have a HAVING w/o a GROUP BY, though the rules about HAVING + GROUP BY will change soon.

2) The first two of these things are for subqueries. See the Hibernate doco.
The third is for accessing collections by index: foo.bars["x"].baz.fum

3) I have no idea. Depends how easy/hard it is, I suppose....