Fuzzy database system refers to a database system that can process fuzzy data. The databases we generally encounter have binary logic and precise data. However, in reality there are many uncertain and ambiguous things. Our brains are also biased towards processing some ambiguous events and are more interested in these ambiguous events. When something is displayed too clearly in front of us, our brain loses the desire to explore it. In this way, incompleteness, uncertainty and fuzziness can be introduced into the database system, thus forming a fuzzy database. Since 1965, when LZ Zade of the United States put forward the fuzzy theory, people have had great interest in this field. The application of fuzzy theory continues to expand, and it has received attention as a popular database.
With the establishment of fuzzy theory system, people can describe fuzzy events with quantity and perform fuzzy operations. In the database system, such achievements in mathematics, such as incompleteness, uncertainty and ambiguity, can also be introduced to form a fuzzy database.
The research of fuzzy database mainly includes two aspects: the first is how to store the fuzzy data in the database, and the second is to define various operations and establish functions on the fuzzy data. The representation methods of fuzzy data mainly include the number of fuzzy intervals, the number of fuzzy centers, the number of fuzzy sets and membership functions.
In a fuzzy database, if each record value is regarded as a node, the relationship is regarded as a connection between nodes. A fuzzy database can be seen as a complex network. The main operation on the fuzzy database refers to the movement from a node to other nodes in the network. But because it mainly involves a strong pointer or cursor to indicate the current position, its complexity will be greatly increased, so the development prospect is not optimistic.
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In the fuzzy hierarchical data model, the intimacy of "parent-child relationship" and "brother relationship" of each node in the tree is realized by membership value. However, like the fuzzy network data model, its complexity also limits the development of fuzzy hierarchical databases.
In the fuzzy relational data model, there are several types, such as tuple fuzzy relational data model, fuzzy relational data model, set-valued fuzzy relational data model and fuzzy relational data model with weighted fuzzy value of attributes. Among them, the fuzzy relational database with weighted fuzzy attributes is the most thorough fuzzy database for one-to-one general relational database fuzzification, and it is the most widely used fuzzy database.
In the fuzzy object-oriented database, the definition of object class introduces the concept of recursion and adopts the object-oriented description method, which has strong modularization and high degree of structure, which is convenient for layered implementation and is beneficial to the development of practical systems. But because it is not yet mature, the development brings great difficulties.
Object-relational data model is a model developed by combining relational data model and object-oriented model. It has the functions of a powerful query language of relational data model, and also has object-oriented features, so it is currently the best choice for building fuzzy databases.