PAT stands for "Persistent Applications Toolkit". Like many other software it simplifies developing of persistence layers of business applications. It does it by providing object-oriented environment for persistence of your objects: POJOs
And.. it really does it.
PAT provides almost transparent data layer for a business application. It employs state-of-the-art techniques to achieve it. These are OO, AOP (JBossAOP), Java, Prevayler, Ant, JUnit, Log4j, @@annotations and others. It cooperates well with web applications: Struts (and possibly other web frameworks), Tomcat, JBoss AS.
(AOP term: persistence aspect)