Referential Actions as Logical Rules
Bertram Ludäscher, Wolfgang May, Georg Lausen
Abstract. Referential actions are specialized triggers used to
automatically maintain referential integrity. While their local
behavior can be grasped easily, it is far from clear what the combined
effect of a set of referential actions, i.e., their global semantics
should be. For example, different execution orders may lead to
ambiguities in determining the final set of updates to be applied. To
resolve these problems, we propose an abstract logical framework for
rule-based maintenance of referential integrity: First, we identify
desirable abstract properties like admissibility of updates
which lead to a non-constructive global semantics of referential
actions. We obtain a constructive definition by formalizing a set of
referential actions RA as logical rules, and show that the
declarative semantics of the resulting logic program
PRA captures the intended abstract semantics: The
well-founded model of PRA yields a unique set of
updates, which is a safe, sceptical approximation of the set of all
maximal admissible updates; the third truth-value undefined is
assigned to all controversial updates. Finally, we show how to obtain
a characterization of all maximal admissible subsets of a given set of
updates using certain maximal stable models.
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