The focus of this research is that in fact a duality does exist between views and constraints (hypothesis 1) and that this duality is a useful tool in the development of information systems (hypothesis 2). Employing both proof and empirical evidence, our investigation reveals that the accuracy with which the first hypothesis holds depends upon the degree to which the constraints can be formalized. In the case of the relational data model, the constraints can be formalized. This is even true of the semantic constraints that are expressible in relational algebra and relational calculus. In the case of the other models that we explore, the constraints have a less formal expression, and views prove to be a method for interjecting more formality into the expression of the constraints.
Our results concerning the accuracy of the first hypothesis also hold for the second hypothesis; that is, the accuracy with which the second hypothesis holds depends upon the degree to which the constraints can be formalized. In the case of the relational data model, the constraints can be formalized, and thus we can generate general solutions for them. Nevertheless, uses of the duality outside the relational domain may be possible, and this is a focus of future work.
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