Extending SQL with customizable soft selection conditions

ABSTRACT

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.

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INDEX TERMS

Primary Classification:
  H. Information Systems
  H.2 DATABASE MANAGEMENT
      H.2.3 Languages

General Terms:
Languages

Keywords:
SQL, flexible query languages, fuzzy set theory