Open and Closed World Assumptions in Data Exchange
Leonid O. Libkin, Cristina Sirangelo · Edinburgh Research Explorer (University of Edinburgh) · 2009
Data exchange is the problem of finding an instance of a target schema, given an instance of a source schema and a specification of a mapping between the source and the target schemas, and answering queries over target instances. A schema mapping is a condition, often expressed in a fragment of first-order logic, that relates instances of source and target schemas. Most commonly it is a conjunction of sentences of the form