is a set of requirements proposed by Christopher J. Date
and Hugh Darwen
in their book The Third Manifesto
for what they believe a relational database query language
ought to be like; D
is not a language itself.
, by itself, refers to a set of requirements proposed by Date and Darwen for what they believe a relational language ought to be like. Tutorial D
is an abstract instantiation of D which is described and used in The Third Manifesto
. It should be noted that it is not required for instantiations of D
to have the same syntax as Tutorial D; just that a "valid D
" must have a certain set of features and exclude a different set of features which Date and Darwen consider unwise. A valid D
may have additional features which are outside the scope of relational databases
Note that this D is distinct from the D language, which is a general purpose programming language.
is an abstract instantiation of D
, described and used in The Third Manifesto
. The purpose of Tutorial D is to show what a D
might be like. Its purpose is educational.
While Tutorial D is an academic
language, any relatively faithful implementation of D meant to be used in the industry
is called an Industrial D
D’s first implementation is D4
, written in C#
. D4 is the flagship language of Alphora
. Others include Rel
, and Dee
. All would be considered "Industrial D"s.