The Third Manifesto (1995) is Christopher J. Date's and Hugh Darwen's proposal for future database management systems, a response to two earlier Manifestos with the same purpose. The theme of the manifestos is how to avoid the 'object-relational impedance mismatch' between object-oriented programming languages and relational database management systems. The Third Manifesto proposes to maintain the relational model for databases and to support objects as user-defined types.
A major theme of the manifesto is to explain how the inadequacies of existing relational database management systems are not shortcomings of the relational database model per se, but rather, of implementation decisions in those systems, and of the SQL query language that most of these systems use.
The manifesto describes an alternative to SQL, named D. D is a specification of desirable characteristics of a database language, rather than a specific syntax or grammar. As such, it describes a family of languages rather than any particular language. However, as an example, a particular member of the hypothetical D "family" called Tutorial D is described in detail, including significant portions of its grammar.
Several partial implementations of D exist, including:
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