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Although a database view embodies partial information about the state of the main schema, the state of the view schema is a quotient (and not a subset) of the state of the main schema. It is the information content of the view state, the set of sentences which are true for that state, and not the state itself which is a subset of the information content of the state of the main schema. There are thus two dual approaches to modelling this partiality, one based upon structures, with a consequent quotient relationship, and another based upon logical theories, with a consequent subset relationship.
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