Before revision: An ED is a sentence in first-order logic of the form:∀x1 ... xn, P(x1, ..., xn) → ∃z1, ..., zk, Q(y1, ..., ym)where z1, ..., zk = y1, ..., ym \ {x1, ..., xn algorithm known as the chase takes as input an instance that may or may not satisfy a set of EGDs (or more generally a set of EDs), and, if it terminates (which is a priori undecidable), output an instance that does satisfy the EGDs.
After revision: An ED is a sentence in first-order logic of the form:∀x1 ... xn, P(x1, ..., xn) → ∃z1, ..., zk, Q(y1, ..., ym)where z1, ..., zk = y1, ..., ym An algorithm known as the chase takes as input an instance that may or may not satisfy a set of EGDs (or , more generally, a set of EDs), and, if it terminates (which is a priori undecidable), output an instance that does satisfy the EGDs.