ON ARMSTRONG DATABASES FOR CONDITIONAL GENERALIZED EMBEDDED DEPENDENCIES

The family of conditional generalized embedded dependencies about relations in relational databases is introduced. These constraints are expressible as formulas in second-order logic and they are constructed with generalized embedded dependencies as the components. For a class of this family a characterisation of a given constraint logically implied by a certain subclass of the class is given. The existence of the Armstrong-like databases for special classes of con ditional generalized embedded dependencies is proved. A method for the construction of an Armstrong model, when it exists and certain condi tions are fulfilled, is given. CR categories: 4.33, 5.21, 5.27, 5.32