Clarifying Transformer interface contract

[Rob Vesse <rv...@dotnetrdf.org>]

Andy

Just wanted to check my understanding of the Transformer interface contract
is correct to ensure I don't incorrectly describe it in my tutorial next
month

My understanding was that Transformer is applied bottom up and that each
call to the transformer receives the original operator and the results of
transforming the sub-operators.  So for example if I'm implement the
transform(OpJoin join, Op lhs, Op rhs) method what I'm getting is the
original join operator plus the results of transforming the inner operators

Thanks,

Rob