closed-world assumption

The assumption that a knowledge baseknowledge base, n.: A store of facts and rules that a program can reason with: like a database, but organized so that new conclusions can be worked out from it, not just looked up. or database contains all relevant positive facts, so that any atomic statement not derivable from it is taken to be false. It lets a system answer negative queries ('Does the library hold a copy of this atlas?' — 'No') without storing negative facts, and it underlies relational databases, DatalogDatalog, prop. n.: A small logic language for asking questions of a database with rules, including rules that refer to themselves, such as 'X is an ancestor of Y if X is a parent of an ancestor of Y'. and the negation-as-failure rule of logic programminglogic programming, n.: A style of programming in which you write down facts and rules in logic and then ask questions; the computer works out the answers itself by logical deduction.. Because adding facts can retract conclusions drawn by default, reasoning under the closed-world assumption is non-monotonicnon-monotonic reasoning, n.: Reasoning in which new information can overturn earlier conclusions — you assume a bird can fly until you learn it is a penguin — as people do constantly but classical logic does not allow.. Its opposite, the open-world assumption, treats underivable statements as merely unknown; it is adopted by first-order logicfirst-order logic, n.: A precise formal language for statements about objects and their relations, using 'for all' and 'there exists', such as 'every person has a mother'. It is the standard logic of mathematics and of classic AI. and by the semantic websemantic web, n.: An effort to label data on the web in a standard, precise way so that programs, not only human readers, can tell what it means and connect facts drawn from many different sites. languages RDFResource Description Framework, prop. n.: A web standard for writing facts as simple three-part statements — subject, relation, object — using web addresses as names, so that data from different sources can be merged automatically. and OWLWeb Ontology Language, prop. n.: A web standard language for writing ontologies — precise definitions of categories and their relationships — so that software can check them for contradictions and infer new facts., where no source is presumed complete — a frequent cause of confusion for users of OWL reasoners.

Under the closed-world assumption the system concluded that the patient has no allergies, simply because none were recorded.