The Model classes are PHP classes responsible only for representing database
entities in memory. For example, the articles table stores article
information in the database; there is a corresponding Model class called
Article (see classes/article/Article.inc.php)
and DAO class called ArticleDAO (see the section called Data Access Objects
[DAOs]).
Methods provided by Model classes are almost exclusively get/set methods to
retrieve and store information, such as the getTitle() and
setTitle($title) methods of the Article class. Model
classes are not responsible for database storage or updates; this is accomplished by
the associated DAO class.
All Model classes extend the DataObject class.