There are three basic data models in the process of data development, namely hierarchical model, network model and relational model. These three models are named after their data structures, and the first two models adopt formatted structures. In this structure, entities are represented by record types, which are abstracted as vertices of a graph, and the relationship between record types is abstracted as connecting arcs between vertices. The whole data structure corresponds to the graph.

The basic structure of hierarchical model is tree structure; The basic structure of grid model is undirected graph without any restrictions. The relational model is an unformatted structure, and the relationship between entities is represented by a single two-dimensional table structure. Relational model is a commonly used data model in database at present.

Constituent element

The content described by data model: data structure, data operation and data constraint.

1. data structure: the data structure in the data model mainly describes the types, contents, attributes and relationships of data. Data structure is the basis of data model, and data operations and constraints are based on data structure. Different data structures have different operations and constraints.

2. Data operation: The data operation in the data model mainly describes the operation type and operation mode on the corresponding data structure.

3. Data constraints: Data constraints in the data model mainly describe the syntax, semantic relations, constraints and dependencies between data in the data structure, as well as the rules of dynamic changes of data to ensure the correctness, validity and compatibility of data.