Type Inheritance and Relational Theory

APPENDIXES

The subject of type inheritance seems mostly to have been investigated in an object context specifically. By contrast, the inheritance model defined by Darwen and myself was constructed from first principles, using a combination of logic, common sense, and well established criteria for language design, and being guided by our background knowledge of relational theory. In particular, we saw no need to appeal to any concepts or mechanisms from the object world, nor did we do so. As a consequence, our solutions to certain inheritance issues differ, sometimes markedly, from approaches discussed in the object literature to those same issues. Appendixes A and B offer a little more by way of background explanation as to why we don’t always agree with those object approaches. Finally, Appendix C provides for purposes of quick reference a glossary of some of the more important terms and concepts involved in our own approach.