This paper focuses on the empirical whole model validation effort bein
g undertaken as part of the CEC PASSYS project, placing it in the cont
ext of an overall validation methodology. High quality datasets lie al
the heart of empirical validation, and reasons are given as to why te
st cells are considered to provide the best available environment for
their acquisition. Criteria are set out that help ensure that the coll
ected datasets are of value for validation, and the various elements o
f an empirical validation methodology are elaborated. Finally, some pr
eliminary results and analysis are presented.