To understand how this circle has been squared Haynes encouraged the PPDM membership to consider that "reality is truth, data models are abstractions". A data model, being a highly normalized structure can be viewed in a number of different ways. The data model plus the observer becomes the View. Such views are part and parcel of database management systems and can allow a programmer to access data in a more domain oriented and comprehensible way. They are nearly Business Objects, except that their scope is limited to the RDBMS in use. GeoFrame currently uses the Epicentre data model in the realm of production where it is said to be "fully compliant" with Epicentre. This implementation of Epicentre has been derived from POSCs logical model using Express, but not the projection tool.
All done by Views!
Projection has been hand coded to ensure a one to one mapping from Epicentre to reconstruct the views of the data that GeoQuests applications are used to seeing. Even with this, integrating these applications, more used to working off of the PPDM derived Finder, has caused some challenges to the programmers. These have been circumvented by defining PPDM Views of the GeoFrame data model for instance a PPDM View of a POSC well completion header. This view is created by a join on 5 different GeoFrame tables and produces a PPDM like data structure. Questions were asked as to the performance hit involved in this additional layer between application and database. John Gillespie of GeoQuest replied that using views was slower than direct table access, but that performance was still adequate. PPDMers pointed out that if GeoQuests applications required a simpler view of the data than Epicentre could provide, then they might as well use PPDM as the physical model. This presumably would not be politically correct.
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