We extend the relational data model to incorporate linear orderings into data domains,which we call the ordered realtional modle.We formally define Ordred Functional Dependencies (OFDs) for the extendded model by means of tow possible extensions of domains,pointwise orderings and lexicographical ordrings.We first present a sound and complete axiom ystem for OFDs in the case of pointwise-orderings and theen establish a et of sound and ocmplete chase rules for OFDs in the case of lexicographical orderings.Our main result shows tha tthe implication problems for both cses of OFDs re decidable,and that it is linear time for the case of poinwise orderings.
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