[coolgeek]

Not all databases are relational. Not all relational databases are built on b-trees.

From the summary:

> Many people are building queue managers on file systems as a transactional resource manager and a TP-lite monitor. An alternative approach is to evolve an Object-Relational database system to support the mechanisms needed to build a queuing system

The key word here is evolve.

The point is to think of a queuing system in the database as a concept sense, rather than the database as a specific implementation sense.