What is a model? A nice definition

Eric Evans, during this talk about Domain-Driven Design (DDD), defines nicely a model as

a system of abstractions that describes selected aspects of a domain and can be used to solve problems related to that domain

CPM tutorial

You can find a nice and practical guide to the Critical Path Method here.

JPA in Eclipse: drop database at each test

If you want to drop your database at each test launch, open the file persistence.xml (under JPA) and modify the following line:

 <property name="javax.persistence.schema-generation.database.action" value="create"/>

to become as follows:

 <property name="javax.persistence.schema-generation.database.action" value="drop-and-create"/>