In Reiter's default logic, the parameters of a default are treated as metavariables for ground terms. We propose an alternative definition of an extension for a default theory, which handles parameters as genuine object variables. The new form of default logic may be preferable when the domain closure assumption is not postulated. It stands in a particularly simple relation to circumscription. Like circumscription, it can be viewed as a syntactic transformation of formulas of higher order logic.

PDF

In Computational Logic: Symposium Proceedings, Lloyd, John (Eds.), pp. 80-95 1990. Springer.

@inproceedings{lif90a, title={On Open Defaults}, author={Vladimir Lifschitz}, booktitle={Computational Logic: Symposium Proceedings}, editor={Lloyd, John}, publisher={Springer}, pages={80-95}, url="http://www.cs.utexas.edu/users/ai-lab?lif90a", year={1990} }