[Mulgara-dev] Query Evaluation - binding variables

[Alex Hall]

I'm trying to write a TQL query to traverse an RDF list using the walk 
function.  I would like to express the anchor for the walk function as a 
variable that is bound by another constraint in the query.  So my TQL 
command looks like this:

select $x $value from <rmi://localhost/server1#model>
   where $x <rdf:type> <owl:AllDifferent>
     and $x <owl:distinctMembers> $y
     and walk($y <rdf:rest> $node and $z <rdf:rest> $node)
     and $node <rdf:first> $value;

However, when I execute this query, I get an error message, 
"org.mulgara.query.QueryException: The subject: $y and the object: $node 
are invalid, one must be a variable and the other a fixed value around a 
predicate."  I know that this can be worked around by using a subquery, 
but I'm hoping to avoid a subquery.  It seems there should be some way 
to force Mulgara to evaluate the first two constraints and bind the 
variable $y to a value before evaluating the walk function.  Am I 
mistaken here?  Any suggestions?

Regards,
Alex