This paper presents an extension of propositional dynamic database logic in which arbitrary database transactions can be specified declaratively. Typically, declaratively specified transactions are under-specified. Specifications are usually supplemented with a frame assumption about what does not change as the result of a transaction, and a qualification assumption stating that transactions occur, provided they respect certain conditions called 'guards' and do not contravene any constraints. In addition these (static) constraints may be, or may not be interpreted to force ramifications of transactions. In the former case, both frame and qualification assumption should also apply to ramifications. We solve these problems by defining preferences over Kripke structures and showing how these can be used to define an intended semantics that, for each declarative transaction specification, selects a unique meaning for each transaction. In particular, the intended semantics formalizes a frame assumption and selects qualifications and ramifications for each specification. The notion of preferential entailment based on the semantics provides a natural way of reasoning about declaratively specified transactions.
|Number of pages||10|
|Publication status||Published - Sep 1996|