Incomplete Information in Relational Databases
Journal of the ACM (JACM)
On the representation and querying of sets of possible worlds
SIGMOD '87 Proceedings of the 1987 ACM SIGMOD international conference on Management of data
PODS '89 Proceedings of the eighth ACM SIGACT-SIGMOD-SIGART symposium on Principles of database systems
Imprecise information and uncertainty in information systems
ACM Transactions on Information Systems (TOIS)
Accommodating imprecision in database systems: issues and solutions
ACM SIGMOD Record - Directions for future database research & development
Handling missing data by using stored truth values
ACM SIGMOD Record
Error propagation in distributed databases
CIKM '95 Proceedings of the fourth international conference on Information and knowledge management
The distributed information search component (Disco) and the World Wide Web
SIGMOD '97 Proceedings of the 1997 ACM SIGMOD international conference on Management of data
A statistical approach to incomplete information in database systems
ACM Transactions on Database Systems (TODS)
Extending the database relational model to capture more meaning
ACM Transactions on Database Systems (TODS)
Scrambling query plans to cope with unexpected delays
DIS '96 Proceedings of the fourth international conference on on Parallel and distributed information systems
Null values in data base management a denotational semantics approach
SIGMOD '79 Proceedings of the 1979 ACM SIGMOD international conference on Management of data
On relational algebra with marked nulls preliminary version
PODS '84 Proceedings of the 3rd ACM SIGACT-SIGMOD symposium on Principles of database systems
A Hybrid Representation of Vague Collections for Distributed Object Management Systems
IEEE Transactions on Knowledge and Data Engineering
Database Access in Mobile Environments
DEXA '96 Proceedings of the 7th International Conference on Database and Expert Systems Applications
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Inaccessibility of part of the database is a research topic hardly addressed in the literature about distributed databases. However, there are various application areas, where the database has to remain operable even if part of the database is inaccessible. In particular, queries to the database should be processed in an appropriate way. This means that the final and all intermediate results of a query in a distributed database system must be regarded as potentially vague. In this paper we propose hybrid representations for vague sets, vague multisets, and vague lists, which address the accessible elements in an enumerating part and the inaccessible elements in a descriptive part. These representations allow to redefine the usual query language operations for vague sets, vague multisets, and vague lists. The main advantage of our approach is that the descriptive part of the representation can be used to improve the enumerating part during query processing.