Fallback value
A parameter, which is demanded by a target page, can be populated by the caller with a value.
It is also possible to string fallback values together in this case. Based on the principle of "first match", the first fallback value to deliver a valid value will be used at run-time. Parameter values, which are the same for all or at least the majority of callers, can already be predefined with values at the target page.
A fallback value chain can also be created here. If the caller does not provide a valid value for the parameter, then the fallback value chain of the target page will be worked through and the first valid value found will be used.
If a valid value for a required parameter cannot be determined for either the caller or the target page, the target page cannot be displayed or used.
All further information on this topic can be found here: