Paper Info
Title
A Practical Approach to Hypothetical Database Queries
Abstract
Hypothetical queries are queries embedding hypotheses about the database. The embedded hypothesis in a hypothetical query indi- cates, so to say, a state of the database intended for the rest of the query. Thus the answer to a hypothetical query h > q, with a hypothesis h, is in principle the result of evaluating q against the database revised with h. In case h is inconsistent with the database, query evaluation becomes a special case of counterfactual reasoning. However, the possi- ble worlds semantics usually applied for this notion is not relevant for database applications due to reasons of ineciency. In this paper we dis- cuss and compare dierent approaches to hypothetical queries, paying special attention to potentials for ecient evaluation. As a central part of the paper we present and discuss our own approach "counterfactual exceptions", which have the important property of, as opposed to the other approaches discussed, requiring only minor overhead in query eval- uation. This approach is thus realistic for practical implementation and use in environments supporting large databases. The "price" for ecient evaluation is an altered semantics, as compared to the other approaches. However, it can be argued that this semantics is at least as appropriate for database applications as that of the other approaches mentioned.
Year
DOI
Venue
1998
10.1007/BFb0055505
Dagstuhl Seminars
Keywords
Field
DocType
practical approach,hypothetical database queries
Query optimization,Data mining,Alias,Query language,Computer science,View,Theoretical computer science,Data integrity,Spatial query,Online aggregation,Database,Special case
Conference
ISBN
Citations 
PageRank 
3-540-65305-8
6
0.46
References 
Authors
16
2
Name
Order
Citations
PageRank
Henning Christiansen158846.57
Troels Andreasen250543.70