Artificial Intelligence Events
The Closed World Assumption: a technical presentation by Chris Date
Location: CS1.04
The Closed World Assumption
a technical presentation
by C. J. Date
ABSTRACT
The Closed World Assumption (CWA) is an extremely important concept in
the database world, despite the fact that it isn't usually spelled out
explicitly. Basically what it says is this: Everything stated by the
database, either explicitly or implicitly, is true; everything else is
false. This presentation explains the CWA in detail and shows why it's
preferred over its rival, the Open World Assumption (OWA). In
particular, it examines the claims that are sometimes heard to the
effect that the database community operates under the CWA while the
semantic web community operates under the OWA. It also explains how
"missing information" can be handled without any need for nulls or
three-valued logic.
Topics
Background review: what a database really is (?)
Relation values vs. relation variables
Relvar predicates and constraints
The CWA and OWA defined
Why the CWA is preferred
Relvar predicates revisited
Unknown and uncertain information
Negation and disjunction
a technical presentation
by C. J. Date
ABSTRACT
The Closed World Assumption (CWA) is an extremely important concept in
the database world, despite the fact that it isn't usually spelled out
explicitly. Basically what it says is this: Everything stated by the
database, either explicitly or implicitly, is true; everything else is
false. This presentation explains the CWA in detail and shows why it's
preferred over its rival, the Open World Assumption (OWA). In
particular, it examines the claims that are sometimes heard to the
effect that the database community operates under the CWA while the
semantic web community operates under the OWA. It also explains how
"missing information" can be handled without any need for nulls or
three-valued logic.
Topics
Background review: what a database really is (?)
Relation values vs. relation variables
Relvar predicates and constraints
The CWA and OWA defined
Why the CWA is preferred
Relvar predicates revisited
Unknown and uncertain information
Negation and disjunction