JCSS 43 (1991), pp 170-218.
A new definition of complex objects is introduced which provides a denotation for incomplete tuples as well as partially described sets. Set values are ``sandwiched'' between ``complete'' and ``consistent'' descriptions (representing the Smyth and Hoare powerdomains respectively), allowing the maximal values to be arbitrary subsets of maximal elements in the domain of the set. We also examine the use of rules in defining queries over such objects.
See here for the paper.
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