The data on the form can be stored in either a field or a variable:

• Each field corresponds to a persistent object property that is loaded from/saved to database.
• Variables are not directly connected to the object in the database. However, variables lifetime is synchronized with the lifetime of the object in the form: it starts when an object is loaded in the form and ends when the object is unloaded.

Both fields and variables can be either editable or calculated:

• Editable field/variable can still have a default value that is calculated when a new object is created.
• Calculated field/variable has its value calculated according to Form Calculation Model.

If a field is editable, it can only be edited when the form is in the edit mode. Variables can be set to be always editable, or editable in the edit mode only.