Functional dependencies in relations with null values
Information Processing Letters
Set-theoretic problems of null completion in relational databases
Information Processing Letters
Theoretical Computer Science
The management of changing types in an object-oriented database
OOPLSA '86 Conference proceedings on Object-oriented programming systems, languages and applications
Semantics and implementation of schema evolution in object-oriented databases
SIGMOD '87 Proceedings of the 1987 ACM SIGMOD international conference on Management of data
Schema evolution and the relational algebra
Information Systems
Temporally oriented data definitions: managing schema evolution in temporally oriented databases
Data & Knowledge Engineering
Schema evolution in database systems: an annotated bibliography
ACM SIGMOD Record
Relational database theory
Schema transformation without database reorganization
ACM SIGMOD Record
Schema evolution in OODBs using class versioning
ACM SIGMOD Record
ACM SIGMOD Record
Schema versioning for multitemporal relational databases
Information Systems
Logical approaches to incomplete information: a survey
Logics for databases and information systems
Problem of Incomplete Information in Relational Databases
Problem of Incomplete Information in Relational Databases
Null values in data base management a denotational semantics approach
SIGMOD '79 Proceedings of the 1979 ACM SIGMOD international conference on Management of data
A View Mechanism for Object-Oriented Databases
EDBT '92 Proceedings of the 3rd International Conference on Extending Database Technology: Advances in Database Technology
The Historical Relational Data Model (HRDM) and Algebra Based on Lifespans
Proceedings of the Third International Conference on Data Engineering
A Transparent Object-Oriented Schema Change Approach Using View Evolution
ICDE '95 Proceedings of the Eleventh International Conference on Data Engineering
On Schema Versioning in Temporal Databases
Proceedings of the International Workshop on Temporal Databases: Recent Advances in Temporal Databases
A Taxonomy for Schema Versioning Based on the Relational and Entity Relationship Models
ER '93 Proceedings of the 12th International Conference on the Entity-Relationship Approach: Entity-Relationship Approach
Functional dependencies and incomplete information
VLDB '80 Proceedings of the sixth international conference on Very Large Data Bases - Volume 6
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After the schema of a relation has evolved some tuples no longer fit the current schema. The mismatch between the schema a tuple is supposed to have and the schema a tuple actually has is inherent to evolving schemas, and is the defining property of legacy tuples. Handling this mismatch is at the very core of a DBMS that supports schema evolution. The paper proposes tuple versioning as a structure for evolving databases that permits conditional schema changes and precisely keeps track of schema mismatches at the level of individual tuples. Together with the change history this allows the DBMS to correctly identify current, legacy, and invalid tuples. We give an algorithm that classifies tuples, in time and space proportional to the length of the change history. We show how tuple versioning supports a flexible semantics needed to accurately answer queries over evolving databases.