  Over a decade ago, the H1 Collaboration decided to embrace the
object-oriented paradigm and completely redesign its data analysis model and
data storage format. The event data model, based on the RooT framework,
consists of three layers - tracks and calorimeter clusters, identified
particles and finally event summary data - with a singleton class providing
unified access. This original solution was then augmented with a fourth layer
containing user-defined objects.
  This contribution will summarise the history of the solutions used, from
modifications to the original design, to the evolution of the high-level
end-user analysis object framework which is used by H1 today. Several important
issues are addressed - the portability of expert knowledge to increase the
efficiency of data analysis, the flexibility of the framework to incorporate
new analyses, the performance and ease of use, and lessons learned for future
projects.
