Developement of PDDI interface:

Though PDDI was a research exercise, this contributed understanding, mechanisms, and models to future standards, mostly notably ISO 10303 - Standard for the Exchange of Product Model Data (STEP).

Added shortcomings were afterwards identified such as:

Subsetting: Vendors chosen and implemented only portions of the whole of IGES, therefore making exchange among two systems impossible without prior agreement on what was to be exchanged.

Conformance Testing: There was no mechanism for or resolving errors or testing processors among two processors.

The PDDI interface was developed in association with the ICAM project that was funded by the Air Force in order to develop the manufacturing methods in the aircraft industry. The necessary goal of this product was the creation of an interface among CAD and CAM. PDDI is design-oriented; this provides a formal specification of a product model and its sub models. The latter represent following:

1. The 3-D geometry of the product that is described by a set of surfaces, curves and volumes.

2. The topology which defined the set of elements and relations for describing the product boundary.

3. The tolerance that is inherent in the accuracy of the manufacturing procedure.

4. The future elements required for defining manufacturing operations.

5. The non-geometric information for organizational reason and description of material and its properties.

Added information involved the specification of the pre- and post-processors required for the data exchange among CAD and CAM. The PDDI efforts were conceptual research activities and the results were utilized for the growth of the PDES activities and are a major input to STEP.