Data Model: Conceptual Data Model, Logical Data Model, physical data model

The data model describes three parts: data structure, data operations, and data constraints.

1) Data Structure: The data structure in the data model mainly describes the data type, content, nature, and connection between data. Data structure is the basis of the data model, and data operations and constraints are built on the data structure. Different data structures have different operations and constraints.

2) Data Operations: Data Operations in the data model mainly describe the operation types and operation methods on the corresponding data structure.

3) Data constraints: Data constraints in a data model mainly describe the syntaxes, word meanings, constraints and dependencies between data in a data structure, and the rules for dynamic data changes, to ensure that the data is correct, valid, and compatible.

Data Models are divided into three types based on different application layers: Conceptual Data Model, Logical Data Model, and physical data model.

1. Concept Data Model (Conceptual Data Model): referred to as the concept Model. It is mainly used to describe the Conceptual structure of the world. It enables database designers in the initial stage of design, instead of the specific technical problems of computer systems and DBMS, you can focus on analyzing data and the relationships between data. This is irrelevant to a specific data Management System (DBMS. The conceptual data model must be replaced with a Logical Data Model before it can be implemented in DBMS.

The conceptual data model is an end user's opinion on data storage and reflects the comprehensive information requirements of end users. It describes enterprise-level data requirements in the form of data, data classes represent several main types of data that are naturally integrated in the business environment.

The concept data model includes the relationship between important entities and entities. The conceptual data model does not include the attributes of an object, nor does it need to define the primary key of an object. This is the main difference between a conceptual data model and A Logical Data Model.

The goal of the conceptual data model is to unify business concepts and serve as a bridge between business personnel and technical personnel to determine the highest level of relationships between different entities.

In the design process of some data models, the conceptual data model is designed together with the Logical Data Model.

 

2. Logical Data Model, such as the Network Data Model and Hierarchical Data Model. This model must be user-oriented and system-oriented. It is mainly used for the implementation of database management systems (DBMS.

The Logical Data Model reflects the point of view of the system analysis designer on data storage and further decomposes and refines the conceptual data model. The Logical Data Model is determined based on business rules. It provides a basic blueprint for the relationship between business objects, data items of business objects, and business objects.

The content of the Logical Data Model includes all objects and relationships. The attributes of each object are determined, the primary keys of each object are defined, and the foreign keys of the objects are specified, which must be normalized.

The goal of the Logical Data Model is to describe the data in as much detail as possible, but it does not consider how the data is physically implemented.

Logical Data Modeling not only affects the direction of database design, but also indirectly affects the performance and management of the final database. If you invest enough in implementing the Logical Data Model, there are many options to choose when designing the physical data model.

3. Physical Data Model (Physical Data Model): Physical Model for short. It is a computer-oriented Physical representation Model that describes the structure of Data on the storage media, it is related not only to the specific DBMS, but also to the operating system and hardware. Each Logical Data Model has a corresponding physical data model. To ensure its independence and portability, DBMS implements most physical data models automatically, while designers only design special structures such as indexing and clustering.

E-R model, extended E-R model, object-oriented model and predicate model are the most commonly used in conceptual data model. The most common logical data types are hierarchical models, mesh models, and relational models.

The physical data model is based on the Logical Data Model. It designs the database architecture based on various technical implementation factors to truly store data in the database.

The content of the physical data model includes determining all tables and columns, defining foreign keys for determining the relationship between tables, and sending the contents such as paradigm based on user requirements. In terms of physical implementation, physical data models and logical data models may be significantly different.

The goal of the physical data model is to specify how to use the database mode to implement the Logical Data Model and truly store data.