Codd's 12 rules
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| Codd's 12 rules | |
|---|---|
| Name | Edgar F. Codd |
| Caption | Edgar F. Codd |
| Birth date | 1923-08-19 |
| Death date | 2003-04-18 |
| Known for | Relational model, twelve rules |
| Occupation | Computer scientist |
| Alma mater | University of Oxford |
| Employer | IBM |
Codd's 12 rules are a set of twelve principles formulated to define what constitutes a true relational database management system, proposed by Edgar F. Codd in 1985. The rules aimed to distinguish relational systems from earlier networked and hierarchical systems and influenced vendors, standards bodies, and academic research across institutions such as IBM, Oracle Corporation, Microsoft, Ingres Corporation, Sybase, PostgreSQL Global Development Group, University of California, Berkeley, Stanford University, and Massachusetts Institute of Technology. The principles were debated and adopted to varying degrees by implementers, standards committees like International Organization for Standardization and American National Standards Institute, and reviewers at venues including ACM SIGMOD and IEEE conferences.
Background and Origin
Edgar F. Codd, an English mathematician and computer scientist trained at University of Oxford and employed by IBM, articulated the relational model in a 1970 paper and later enumerated twelve rules in a 1985 publication to define a relational DBMS. The rules emerged amid competition between systems from IBM, Oracle Corporation, Ingres Corporation, Unisys, Digital Equipment Corporation, Sybase, Microsoft, Informix, Teradata, SAP SE, Bull SAS, Hewlett-Packard, Sun Microsystems, Apple Inc., At&T, Bell Labs, Xerox PARC, Los Alamos National Laboratory, and academic prototypes at University of California, Berkeley, Stanford University, Carnegie Mellon University, Massachusetts Institute of Technology, University of Toronto, University of Cambridge, University of Waterloo, Princeton University, Columbia University, Cornell University, University of Michigan, University of Illinois Urbana-Champaign, University of Washington, California Institute of Technology, and Yale University. Codd’s rules responded to criticisms and commercial claims from vendors showcased at trade fairs and discussed in journals such as Communications of the ACM and IEEE Transactions on Software Engineering.
The Twelve Rules
Codd labeled his principles as rules 0 through 11; they cover data representation, guaranteed access, systematic treatment of nulls, view updating, dynamic online catalogues, high-level insert/update/delete, physical data independence, logical data independence, integrity independence, distribution independence, non-subversion, and rule 0 asserting that a system must be relational. These items were intended to guide implementers including IBM, Oracle Corporation, Microsoft, Ingres Corporation, Sybase, PostgreSQL Global Development Group, MySQL AB, MariaDB Corporation, Teradata Corporation, Amazon Web Services, Google LLC, Facebook, Inc., Twitter, Inc., LinkedIn Corporation, Salesforce, SAP SE, MongoDB, Inc., Couchbase, Redis Labs, Cloudera, Hortonworks, MapR Technologies, Palantir Technologies, Splunk Inc., Tableau Software, SAS Institute, VMware, Inc., Oracle Corporation's R&D groups, and academic projects at MIT, Stanford University, UC Berkeley, Princeton University, and Carnegie Mellon University. The rules were discussed in standards forums of International Organization for Standardization and American National Standards Institute, and cited in textbooks by publishers like Addison-Wesley and O’Reilly Media.
Impact on Relational Database Systems
Codd’s formulation shaped product roadmaps at Oracle Corporation, IBM, Microsoft, Ingres Corporation, Sybase, PostgreSQL Global Development Group, MySQL AB, MariaDB Corporation, Teradata Corporation, Amazon Web Services, Google LLC, Snowflake Inc., Cloudera, Hortonworks, SAP SE, SAS Institute, Tableau Software, Red Hat, Inc., Canonical Ltd., HP Enterprise, Dell Technologies, and influenced standards from ISO/IEC. The rules influenced research at universities such as MIT, Stanford University, UC Berkeley, Carnegie Mellon University, Princeton University, University of Cambridge, University of Oxford, and laboratories at Bell Labs and Xerox PARC. Adoption led to features like declarative SQL interfaces standardized by American National Standards Institute and ISO, transactional guarantees inspired by models discussed in ACM SIGMOD and VLDB conferences, and architectural shifts toward client-server deployments promoted by Sun Microsystems and DEC.
Criticisms and Limitations
Critics from vendor engineering teams at Oracle Corporation, IBM, Microsoft Research, Sybase, Ingres Corporation, MongoDB, Inc., Couchbase, Redis Labs, Cloudera, Hadoop contributors, and academics at MIT, Stanford University, UC Berkeley, Carnegie Mellon University, University of Washington, Princeton University, University of Cambridge, Oxford University Press-affiliated authors, and commentators in Communications of the ACM argued that strict adherence was impractical for performance, distribution, and new workloads. Debates at ACM SIGMOD, VLDB, IEEE workshops, and panels involving representatives from Oracle Corporation, IBM, Microsoft, Google LLC, Amazon Web Services, Facebook, Inc., Twitter, Inc., LinkedIn Corporation, and Netflix, Inc. highlighted trade-offs with NoSQL systems from MongoDB, Inc., Cassandra, HBase, Redis Labs, and streaming platforms like Apache Kafka championed by Confluent, Inc.. Scholars from Harvard University, Yale University, Columbia University, Cornell University, Princeton University, and University of California, Berkeley analyzed limitations in contexts such as big data, eventual consistency, and schema-less storage.
Implementations and Compliance Levels
No mainstream commercial product met all twelve rules completely; vendors including Oracle Corporation, IBM, Microsoft, Ingres Corporation, Sybase, Teradata Corporation, PostgreSQL Global Development Group, MySQL AB, MariaDB Corporation, Amazon Web Services, Google LLC, Snowflake Inc., SAP SE, SAS Institute, and research systems at MIT, Stanford University, UC Berkeley, Carnegie Mellon University, Princeton University, and University of Cambridge claimed partial compliance. Standards efforts at ISO/IEC and implementation case studies in journals like Communications of the ACM and IEEE Transactions on Knowledge and Data Engineering catalogued compliance metrics, while commercial compliance auditing was offered by firms like Gartner, Inc., Forrester Research, and consultancy groups within Accenture, Deloitte, PricewaterhouseCoopers, Ernst & Young, and KPMG.
Legacy and Influence on Modern Data Models
Codd’s twelve rules left a durable imprint on commercial systems from Oracle Corporation, IBM, Microsoft, PostgreSQL Global Development Group, MySQL AB, MariaDB Corporation, Teradata Corporation, Amazon Web Services, Google LLC, Snowflake Inc., SAP SE, Cloudera, Hortonworks, MongoDB, Inc., Couchbase, Redis Labs, Confluent, Inc., Databricks, Inc., Palantir Technologies, and on academic curricula at MIT, Stanford University, UC Berkeley, Carnegie Mellon University, Princeton University, Harvard University, Yale University, Columbia University, Cornell University, University of Cambridge, and University of Oxford. The rules informed the development of SQL standards, influenced the design of NewSQL projects, and provided a reference point for debates about consistency models in distributed systems discussed in venues such as ACM SIGCOMM, ACM SIGMOD, VLDB, and USENIX. Codd’s work continues to be cited in textbooks published by Addison-Wesley, O’Reilly Media, and in standards documents of ISO and ANSI.