Technical Reports (CIS)

Document Type

Technical Report

Date of this Version

February 1994


University of Pennsylvania Department of Computer and Information Science Technical Report No. MS-CIS-94-04.


The Abiteboul and Beeri algebra for complex objects can express a query whose meaning is transitive closure, but the algorithm naturally associated to this query needs exponential space. We show that any other query in the algebra which expresses transitive closure needs exponential space. This proves that in general the powerset is an intractable operator for implementing fixpoint queries.



Date Posted: 25 July 2007