Two major features of the eXpressApp Framework are automatic UI construction, and the ability to produce applications for different target platforms using the same business logic. This means that visual elements in your application are automatically generated, based on data classes and other special class types you have declared. So, the eXpressApp Framework scans the application code, extracts the desired classes, analyzes them, and then builds the database structure and user interface. The result of class declaration analysis is the creation of metadata - data that defines database structure and application features via a neutral format, that can be adopted to any target platform. This metadata is called the Application Model. It is a powerful tool that allows you to customize your application both at design and runtime.
If you used eXpressApp Framework before the version 2010 vol 1 release, you will see that the Application Model concepts changed significantly since this release. The eXpressApp Framework v10.1 Application Model Migration Guidelines knowledge base article describes how to migrate your XAF application to the new Application Model.
To learn more about the Application Model, please refer to the following topics: