Five distinct types of database uncertainty :
Uncertainty -- There might be uncertainty about the database fact " the age of john is 38"
Imprecision -- The information in the model is not as specific as it should be. For example, when distinct value is required, the information available might be:
range : " The age of john is between 37 and 43"
disjunctive: " The age of john is either 37 or 43"
negative : " The age of john is not 37"
unknown : "unknown" i।e। null
Vagueness -- The model includes elements (e.g predicates or quantifiers) that are inherently vague i.e. " John is in early middle age".
Inconsistency-- The model contains two or more alternatives that cannot be true at the same time e.g. " the age of john is between 37 and 43" and the "age of john is 35".
Ambiguity -- Some elements of the model lack complete semantics leading to several possible interpretations e.g. " employees' commission are given per month or per year" .
Ref: Amihai Motro, Management of Uncertainty in database Systems.
