Type consistency of queries in an object-oriented database system

Queries in object-oriented databases can return non-homogeneous sets of objects when no type restrictions are placed on the inputs to the query. The tradition has been to force homogeneity on the result by restricting the types of the inputs. This restricts the range of permissible, and possibly useful, queries. We propose a type consistency theory for queries in object-oriented databases which supports the existence of multiple types in the query result. The technique is illustrated by developing type inference rules for an object algebra. The main result is that the loss of type information associated with a query operation is reduced in most cases. We also show how type information is increased when queries are qualified by conjunctive predicates.

[1]  Michael Stonebraker,et al.  The design of POSTGRES , 1986, SIGMOD '86.

[2]  共立出版株式会社 コンピュータ・サイエンス : ACM computing surveys , 1978 .

[3]  Jay Banerjee,et al.  Queries in object-oriented databases , 1988, Proceedings. Fourth International Conference on Data Engineering.

[4]  Peter Buneman,et al.  Types and persistence in database programming languages , 1987, CSUR.

[5]  Stanley B. Zdonik Data Abstraction and Query Optimization , 1988, OODBS.

[6]  Dave Thomas,et al.  An exemplar based Smalltalk , 1986, OOPSLA 1986.

[7]  Irving L. Traiger,et al.  System R: A Relational Approach to Data Base Management , 1976, Berkeley Workshop.

[8]  Stanley B. Zdonik,et al.  A query algebra for object-oriented databases , 1990, [1990] Proceedings. Sixth International Conference on Data Engineering.

[9]  Hans-Jörg Schek,et al.  A Relational Object Model , 1990, ICDT.

[10]  David Maier,et al.  Development of an object-oriented DBMS , 1986, OOPLSA '86.

[11]  Larry Carter,et al.  Distrbution and Abstract Types in Emerald , 1987, IEEE Transactions on Software Engineering.

[12]  Irving L. Traiger,et al.  System R: relational approach to database management , 1976, TODS.

[13]  David Maier,et al.  Indexing in an Object-Oriented DBMS , 1986, OODBS.

[14]  Luca Cardelli,et al.  On understanding types, data abstraction, and polymorphism , 1985, CSUR.

[15]  Thierry Despeyroux,et al.  Executable Specification of Static Semantics , 1984, Semantics of Data Types.

[16]  Alexander Borgida Class Hierarchies in Information Systems: Sets, Types, or Prototypes? , 1985, Data Types and Persistence.

[17]  Matthias Jarke,et al.  Query Optimization in Database Systems , 1984, CSUR.

[18]  Luca Cardelli,et al.  A Semantics of Multiple Inheritance , 1984, Inf. Comput..

[19]  Scott Danforth,et al.  Type theories and object-oriented programmimg , 1988, CSUR.

[20]  M. Tamer Özsu,et al.  Queries and query processing in object-oriented database systems , 1990, TOIS.