A framework for expressing and combining preferences
SIGMOD '00 Proceedings of the 2000 ACM SIGMOD international conference on Management of data
A relational model of data for large shared data banks
Communications of the ACM
An Overview of Cooperative Answering in Databases
FQAS '98 Proceedings of the Third International Conference on Flexible Query Answering Systems
Qualified Answers That Reflect User Needs and Preferences
VLDB '94 Proceedings of the 20th International Conference on Very Large Data Bases
Preference formulas in relational queries
ACM Transactions on Database Systems (TODS)
Foundations of preferences in database systems
VLDB '02 Proceedings of the 28th international conference on Very Large Data Bases
SQLf: a relational database language for fuzzy querying
IEEE Transactions on Fuzzy Systems
Generalization of strategies for fuzzy query translation in classical relational databases
Information and Software Technology
A Knowledge-Based Approach for Answering Fuzzy Queries over Relational Databases
KES '08 Proceedings of the 12th international conference on Knowledge-Based Intelligent Information and Engineering Systems, Part II
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Users of information systems are aware that databases can be a mine of useful information, and would like to express flexible queries over the data possibly retrieving, not perfect" items when the perfect ones, those exactly matching the selection conditions, are not available. Most commercial DBMSs are still based on the SQL for querying. Thus providing some flexibility to SQL can help users to improve their interaction with the systems without requing them to learn a completely novel language. In our approach we allow vague selection conditions based on linguistic predicates, i.e. soft conditions. This topic has been considered in previous works, specifically in SQL/f which is a proposal for extending SQL with soft conditions; however, we think that SQL/f does not completely solve the problem mainly because it does not provide any practical means to customize the meanings of soft conditions to fit specific application domains. Based on these considerations, we propose an extension of SQL which supports customizable soft selection conditions which admit degrees of satisfaction; customizable soft conditions can be defined by users for their specific needs and application domains by means of an SQL like operator. Specifically, this paper proposes an extension of the basic SQL SELECT operator for specifying soft conditions; introduces a new operator for customizing the semantics of the linguistic predicates, provides the formal semantics for the proposed extension of selection conditions.