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. In accordance with the "first match" principle, the fallback value that first returns a valid value is used at runtime. 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, the fallback value chain of the target page is run through and the first valid value is 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: