D (data language specification)

D is a set of prescriptions for what Christopher J. Date and Hugh Darwen believe a relational database management system ought to be like. It is proposed in their paper The Third Manifesto, first published in 1994 and elaborated on in several books since then.

Overview

D by itself is an abstract language specification. It does not specify language syntax. Instead, it specifies desirable and undesirable language characteristics in terms of prescriptions and proscriptions. Thus, D is not a language but a family of both implemented and future languages. A "valid D" must have a certain set of features, and exclude a different set of features which Date and Darwen consider unwise and contrary to the relational model proposed by E. F. Codd in 1970. A valid D may have additional features which are outside the scope of relational databases.

Tutorial D

Tutorial D is a specific D which is defined and used for illustration in The Third Manifesto. Implementations of D need not have the same syntax as Tutorial D. The purpose of Tutorial D is both educational and to show what a D might be like. Rel is an implementation of Tutorial D.

Implementations

D's first implementation is D4, written in C#. D4 is the flagship language of Alphora's Dataphor. Others include Rel (see above), Opus, Duro, and Dee.

References

• C. J. Date and Hugh Darwen (2007, Addison-Wesley) Databases, Types, and the Relational Model: The Third Manifesto, a third edition superseding first and second editions that are the two books listed below. ISBN 0-321-39942-0

External links

• The Third Manifesto
• Tutorial D , (Chapter 11 of Database Explorations with some minor revisions)
• Tutorial D grammar in alphabetical order of BNF terms
• ALGEBRA, an abstract relational algebra, A, referenced in the definition of Tutorial D.

• Alphora
• Rel - An Implementation of Date and Darwen's database languageTutorial D.
• Duro - a relational database management system
• Dee - makes Python relational
• TclRal - Tcl Relational Algebra Library, TclRal is an implementation of relational algebra, based on concepts in The Third Manifesto, as an extension of the Tcl language.
• Alf - Relational Algebra at your Fingertips, a Ruby implementation of relational algebra inspired by Tutorial D, that you can try online.