A noteworthy built-in abstract model is mail.thread, which is provided by the mail (Discuss) add-on module. On models, it enables, the discussion features that power the message wall that's seen at the bottom of many forms.

Other than AbstractModel, a third model type is available: models.TransientModel. This has a database representation like models.Model, but the records that are created there are supposed to be temporary and regularly purged by a server-scheduled job. Other than that, Transient models work just like regular models.

The models.TransientModel is useful for more complex user interactions, known as wizards. The wizard is used to request inputs from the user. In Chapter 9, Advanced Server-Side Development Techniques, we explore how to use these for advanced user interaction.