All non-recognized parameters in the Physics parameter set shall be interpreted as paths. Something that cannot be a path (e.g. a non-sequence) shall cause an exception to be thrown.
A path shall be interpreted as a trigger path or an end path depending on its contents. A path referring to both observers (outputs and analyzers) and modifiers (producers and filters) shall cause an exception to be thrown.
The content and validity of paths shall be determined without the need for module construction.
trigger_paths will be ignored if specified.
end_paths will be ignored if specified.
The order of specification of paths shall be irrelevant.
The order of specification of modules in an end path shall be irrelevant.
Specification of multiple end paths shall be interpreted as if one end path were specified whose contents were the union of each component end path.