Re: What is a "data sublanguage"

From: Knowledgy <>
Date: Tue, 25 Dec 2007 12:10:56 -0500
Message-ID: <>

In relational database theory, the term sublanguage, coined by E. F. Codd in 1970, refers to a computer language used to define or manipulate the structure and contents of a relational database management system (RDBMS). Typical sublanguages associated with modern RDBMS's are QBE (Query by Example) and SQL (Structured Query Language). In 1985, Codd encapsulated his thinking in twelve rules which every database must satisfy in order to be truly relational. The fifth rule is known as the Comprehensive data sublanguage rule, and states:

A relational system may support several languages and various modes of terminal use (for example, the fill-in-the-blanks mode). However, there must be at least one language whose statements are expressible, per some well-defined syntax, as character strings, and that is comprehensive in supporting all of the following items:
Data definition
View definition
Data manipulation (interactive and by program) Integrity constraints
Transaction boundaries (begin, commit, and rollback)

John K
Knowledgy Consulting, LLC
Atlanta's Business Intelligence and Knowledge Management Experts

"David Cressey" <> wrote in message 

> It's time for me to ask another dumb question.
> The term "data sublanguage" appears in Codd's 1970 paper. I kind of
> glossed
> over it when I first read it, figuring that my intuitive grasp was close
> enough. Now I'm wondering whether I really know what "data sublanguage"
> means, at all.
> What is a "data sublanguage"? What is the difference between a
> "sublanguage" and a "language"? Can a programming language embed a data
> sublanguage as a subset of the syntax and semantics of the programming
> language? Does the data sublanguage Codd was referring to span all the
> syntax and semantics of the relational data model?
> Did SQL take the place of the data sublanguage Codd was suggesting should
> be
> built? Have Date & Darwen or others created a relational data
> sublanguage?
Received on Tue Dec 25 2007 - 18:10:56 CET

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