The properties are set by the server or are modified by actions that the client performs on the controls, for example the ORA_PID_VALUE property will be changed to the next value of a text control if the user alters the control's content.
You can access the property values of each control in your application. There are several OraFormsGetProp{Type} functions that allow you to retrieve the values of certain properties that are identified by their unique ID's.
It is not possible to change properties in a direct way. Properties are changed via various API functions that allow you to interact with controls as a user would in a user interface.