A list of properties for this app. Properties include input parameters for the app, options to determine look and feel, such as width, or options to control other behavior. For more information and examples of declaring properties, setting property values or retrieving properties or property values, see Declare, Get and Set Properties in Custom Apps.

Properties are also used to define the payload or data that the app may publish to other apps or receive from other apps. The payload is defined in <topic> elements. Properties for topic payloads may be complex, containing other properties in any structure needed. See Declare App Topics and Payloads for more information and examples.