PowerDesigner concept Data Model CDM

The concept Data Model (Conceptual Data Model) is also known as the information Model. It is based on the object-link theory and expanded. It models the information Data from the user's perspective, it is mainly used for Conceptual Design of databases. People abstract the real world into a conceptual world, and then convert conceptual data into a computer-understandable model;

CDM is a set of strictly defined model elements that accurately describe the static characteristics, dynamic characteristics, and integrity constraints of the system, it contains three parts: data structure, data operation, and integrity constraint;

General features of the data model:

1. Data feature abstraction in the real world;

2. It simulates the real world;

3. easy to understand;

4. Convertible, implemented by computer;

Drawing the CDM diagram when the customer purchases the product

Create CDM

Create entity

Attribute settings

Feature Recognition

Select the primary (secondary) identifier attribute check box (define different identifiers for each object)

Create data items that can be attached to an object as attributes of the object (minimum unit of information storage)

 

Set Unique code options and Reuse options for data items: Unique code. Each data item has a Unique code in the same namespace. Allow Reuse can act as attributes of multiple objects;

 

An object is successfully drawn.

The relationship between multiple entities. If one end of a line is split, multiple ends are represented. If one end is not split, one end is represented as one. If one end of a small circle is selected, the other end of a small cross is forced;

Multiple entities are successfully drawn.