A Conserative Property of a Nested Relational Query Language

We proposed in [7] a nested relational calculus and a nested relational algebra based on structural recursion [6,5] and on monads [27,16]. In this report, we describe relative set abstraction as our third nested relational query language. This query language is similar to the well known list comprehension mechanism in functional programming languages such as Haskell [ll], Miranda [24], KRC [23], etc. This language is equivalent to our earlier query languages both in terms of semantics and in terms of equational theories. This strong sense of equivalence allows our three query languages to be freely combined into a nested relational query language that is robust and user-friendly. Comments University of Pennsylvania Department of Computer and Information Science Technical Report No. MSCIS-92-59. This technical report is available at ScholarlyCommons: http://repository.upenn.edu/cis_reports/472 A Conservative Property Of A Nested Relational Query Language MS-CIS-92-59 LOGIC & COMPUTATION 48