Turning The Partial-Closed World Assumption Upside Down
نویسندگان
چکیده
The partial-closed world setting provides an intermediate ground between open-world and closed-world settings. Previous work on the partial-closed world assumption assumes that incompleteness is the default, i.e., that databases in general can be incomplete, and are only definitely complete in specified parts. In this work we turn this assumption around, and study databases where completeness is the default, and incompleteness only occurs in specified parts. We present four languages for describing potentially incomplete parts of databases, full-table statements, patterns, local statements and query statements. We show that except for full-table statements, it is not possible to translate between the two settings without extending the languages. Finally, we present techniques to decide query completeness entailment for each of the languages both on the schema and instance level, finding that for queries under bag semantics, the complexity is sometimes easier than under the setting where complete parts are specified.
منابع مشابه
Turning water into rock: The inverted waves effect
Humans perceive shape in two-dimensional shaded images, and turning such an image upside down can result in inversion of the relief of this image. Previous research indicates that this inversion is caused by assumptions related to overhead illumination, global convexity and viewpoint above the surface. In our article, we describe the inverted waves effect, in which turning an image of waves ups...
متن کاملDatabases under the Partial Closed-world Assumption: A Survey
Databases are traditionally considered either under the closedworld or the open-world assumption. In some scenarios however a middle ground, the partial closed-world assumption, is needed, which has received less attention so far. In this survey we review foundational and work on the partial closed-world assumption and then discuss work done in our group in recent years on various aspects of re...
متن کاملA Top-Down Query Answering Procedure for Normal Logic Programs Under the Any-World Assumption
The Any-World Assumption (AWA) has been introduced for normal logic programs as a generalization of the well-known notions of Closed World Assumption (CWA) and the Open World Assumption (OWA). The AWA allows any assignment (i.e., interpretation), over a truth space (bilattice), to be a default assumption and, thus, the CWA and OWA are just special cases. To answer queries, we provide a novel an...
متن کاملQuery Answering under the Any-World Assumption for Normal Logic Programs
Recently, in (Loyer & Straccia 2005) the Any-World Assumption (AWA) has been introduced for normal logic programs as a generalization of the well-known notions of Closed World Assumption (CWA) and the Open World Assumption (OWA). The AWA allows any assignment (i.e. interpretation), over a truth space (bilattice), to be a default assumption and, thus, the CWA and OWA are just special cases. Whil...
متن کاملExplicit Negation in Relational
Negative facts in relational databases have traditionally been inferred using the closed world assumption. There are situations where this is not appropriate. We need to resort to the open world assumption, where the negative facts are sometimes explicitly stated. We present a formalism which is capable of answering queries in the relational database context under the open world assumption. We ...
متن کامل