The Site Object Model
Your Property Definitions, ContentObject Types, and Content Objects are your Site Object Model. Your Site Object Model forms the basis for the application logic of your site and allows you to separate this from your presentation layer. The Site Object Model components have their own security that doesn't rely on presentation layer security, allowing fine control over functionality permissions.
All components of your Site Object Model are uniquely identified and are portable, allowing you to migrate easily from development to staging and on to production. The Site Object Model is constructed by the Interactive Developers and is used as underlying functionality by all other roles in the Spectrum of Participants.