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I have just published a new PRACTICAL DATABASE FOUNDATIONS paper. See the PAPERS page for pricing and ordering information.

Domains: The Database Glue 

Abstract: Domains are a fundamental database feature. Codd, the inventor of the relational model referred to them as the "glue that holds the database together". Mathematical relations are defined on domains and, therefore, so are their database representations, R-tables. Yet they are one of the least understood database features. This is both a cause and a consequence of the failure by SQL DBMS's to implement them truly and fully. The negative implications e.g., weak support for complex and/or user-defined data types" is claimed a weakness of the relational model, rather than an industry implementation failure. This paper

• Defines and explains the domain concept;
• Distinguishes between domains and data types;
• Discusses kinds of domains;
• Clarifies DBMS domain support;
• Discusses practical implications for database and DBMS design.

Table of Contents