This chapter introduces a fuzzy object-relational database model including fuzzy extensions of the basic object-relational databases constructs, the user-defined data types, and the collection types. The fuzzy extensions of these constructs focus on two main flexible aspects, a way to flexibly compare complex data types and an extension of collection types allowing partial membership of its elements. Collection operators are also adapted to consider flexibly comparable domains for its elements. Such a fuzzy object-relational database model, and its implementation in a fuzzy object-relational database management system, provides an easy and effective way to manage a great amount of complex fuzzy data in object-relational databases for emerging fuzzy applications. As a sample of the proposal advantages, an application for dominant color based image retrieval, which is built on an object-relational database management system implementing the proposed fuzzy database model, is introduced.
Key Terms in this Chapter
Flexible Query: A query whose restrictions, or conditions, are weakly defined. Usually, the restrictions of this kind of queries are modeled as fuzzy sets. The results for this query are allowed to partially match the conditions of the query.
Soft Data Server Database Model (SDSDM): A fuzzy object-relational database model that supports fuzzy versions of the basic object-relational database type constructs, the user-defined data types and the collection data-types.
Fuzzy Database: A database able to store and handle imperfect information, which is modeled by taking advantage of fuzzy set theory.
Flexible Equivalence Relation: A fuzzy relation between the values of a database data type that is a flexible replacement of the classical equivalence relation.
Flexibly Comparable Type: A user defined type which encapsulates an implementation of its flexible equivalence relation as a special method. The values of this type can be flexibly compared, so the result of the comparison is a numerical resemblance degree rather than the Boolean value returned by the classical equality comparator.
Fuzzy Collection: A fuzzy set whose elements are of a domain on which a flexible equivalence relation is defined. The operators on this kind of fuzzy set take into account this flexible equivalence relation when correlating domain elements.
Object-Relational Databases: A database whose model is the relational database model but enriched to allow entity attributes to be of complex data type.
Object Data Management Group (ODMG): A group of database vendors and practitioners founded with the aim to increase portability of customer software across object-oriented data management products.
Fuzzy Object-Relational Databases: An extension of object-relational databases to allow them to store and handle fuzzy data.