Here's some
background information on using strings to model hierarchies in SQL.
Unfortunately LIKE doesn't utilize indexes in PostgreSQL if the installation's collation sequence isn't set to "C", as is true for folks using non-Latin character sets. So my implementation uses BIT VARYING which are treated like VARCHARs restricted to '0' and '1'. In Oracle, the Forums package implements tree_sortkeys using the RAW datatype.
You might want to reference that article in your doc.
And my name's spelled "Baccus" :)
