Other Database Models

Besides relational database models and object database models there are a number of other structures suited for specific purposes:

• Flat Model
• Hierarchial Model
• Network Model
• Post Relational Model
• Fuzzy Databases

Flat Model

The flat [or table] model consists of a single, two-dimensional array of data elements, where all members of a given column are assumed to be similar values, and all members of a row are assumed to be related to one another.

Hierarchical Model

In a hierarchical model, data is organized into a tree-like structure, implying a single upward link in each record to describe the nesting, and a sort field to keep the records in a particular order in each same-level list.

Network Model

The network model tends to store records with links to other records. Associations are tracked via "pointers". These pointers can be node numbers or disk addresses. Most network databases tend to also include some form of hierarchical model.

Post-relational Database Models

Post-relational data models incorporate relations unconstrained by the Information Principle, requiring that all information is represented by data values in relations. Examples include PICK [MultiValue] and MUMPS.

Fuzzy Databases

A Fuzzy relational databases is a database using fuzzy logic, [fuzzy attributes], which may be defined as attributes of imprecise or uncertain data. There are many forms of adding flexibility in fuzzy databases. Fuzzy values may be stored in fuzzy attributes using fuzzy sets (including fuzzy spatial datatypes), possibility distributions or fuzzy degrees associated to some attributes and with different meanings (membership degree, importance degree, fulfillment degree...). Fuzzy querying languages have been defined [SQLf] to include fuzzy aspects in the SQL statements, like fuzzy conditions, fuzzy comparators, fuzzy constants, fuzzy constraints, fuzzy thresholds, linguistic labels and so on.

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