Introduction

In this Chapter we describe the relationship between HRDM and the logic ILs and its model theory. This relationship is first presented formally, and is then followed by an informal discussion that emphasizes insights that it can provide into the way that a database models the real world, and into the nature of entities and relationships, of key and non-key attributes, of queries and data constraints, and of the interaction of time with all of these concepts. The formalism is presented in the interests of completeness and rigor, but it is easy to get lost in some of the notation; the informal discussion provides a better overview both of how the temporal dimension is incorporated into, and how it affects, the traditional relational model.

In Chapter 2 we described the syntax and semantics of the language ILs. To be more precise we should rather say the family of ILs languages, any particular language in this family being determined by the set C of non-logical constants. The historical relational database concept presented in Chapter 3 will now be related to the discussion of the intensional logic as follows. First we show that a particular HRDB scheme defines a particular logic in the family of ILs languages that provides a formal expression of the historical database semantics and that serves as the target language for translations from our English Query Language which will be described in the latter half of this work.