You would think that compliance was an unequivocally good thing that everyone would support. Life is not so easy. Terms of reference of PPDM compliance are not intended to be compulsory, nor to guarantee interoperability. Four stages are proposed in the path to compliance, a self check, a tweaking, submission to PPDM and validation and publishing on the PPDM website. Compliance is not a yes/no affair and is measured as a ratio of compliant vs. non-compliant elements. The target for compliance is pre-determined (and will be published) as the footprint of the full PPDM model to be covered by the applicant. Two levels of compliance are envisaged Gold level requires table level read/write compatibility with published PPDM tables, Silver level allows for view defined read only compliance.
Middleware
An interesting issue that arose in discussions was the situation for middleware mapping software such as SAS GEO, here the software assures interoperability, but the internal model does not need to be compliant with any particular model. The issue of minimal compliance as suggested here versus full interoperability was raised, with a reference data set supplied, and a compliance judged by performance of a set of SQL test queries. This leads to the issue of improved or enhanced versions of the model which may work better, but fail compliance testing. These issues are crucial to the whole role of standard data models, they were set up to allow for interoperability, but focus, for PPDM or POSC has gradually drifted such that both organizations play a strange role supporting commercial software developers who use the fruits of the labor of the standardization organizations to their own ends, and now may be dragging their feet over interoperability with any software except their own.
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