  The extensible N-Dimensional Data Format (NDF) was designed and developed in
the late 1980s to provide a data model suitable for use in a variety of
astronomy data processing applications supported by the UK Starlink Project.
Starlink applications were used extensively, primarily in the UK astronomical
community, and form the basis of a number of advanced data reduction pipelines
today. This paper provides an overview of the historical drivers for the
development of NDF and the lessons learned from using a defined hierarchical
data model for many years in data reduction software, data pipelines and in
data acquisition systems.
