Forgive me if this sounds pedantic, but how do you distinguish between DDL and SQL scripts? I only ask because I use a single directory (sql, although I like ddl as well) for this. Aren't they the same thing?
I also wonder if you have a sibling dml directory which has the definitions for a SQL phrasebook. To be honest, that idea only just occurred to me, but it does seems attractive. Something like:
+--sql +--dml # database setup scripts and definitions here. +--ddl # data files with phrasebook definitions here.