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Normal Forms And Conservative Extension Properties For Query Languages Over Collection Types (1995)
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| Venue: | Journal of Computer and System Sciences |
| Citations: | 30 - 8 self |
BibTeX
@ARTICLE{Wong95normalforms,
author = {Limsoon Wong},
title = {Normal Forms And Conservative Extension Properties For Query Languages Over Collection Types},
journal = {Journal of Computer and System Sciences},
year = {1995},
volume = {52},
pages = {495--505}
}
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Abstract
Strong normalization results are obtained for a general language for collection types. An induced normal form for sets and bags is then used to show that the class of functions whose input has height (that is, the maximal depth of nestings of sets/bags/lists in the complex object) at most i and output has height at most o definable in a nested relational query language without powerset operator is independent of the height of intermediate expressions used. Our proof holds regardless of whether the language is used for querying sets, bags, or lists, even in the presence of variant types. Moreover, the normal forms are useful in a general approach to query optimization. Paredaens and Van Gucht proved a similar result for the special case when i = o = 1. Their result is complemented by Hull and Su who demonstrated the failure of independence when powerset operator is present and i = o = 1. The theorem of Hull and Su was generalized to all i and o by Grumbach and Vianu. Our result generali...
Keyphrases
normal form conservative extension property query language collection type powerset operator van gucht nested relational query language intermediate expression set bag list induced normal form general approach general language collection type similar result complex object maximal depth strong normalization result result generali special case variant type
