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This article mainly introduces what are the knowledge points of UML object graph, which can be used for reference by interested friends. I hope you can learn a lot after reading this article.

UMl object graph

I. Overview

Object graph (ObjectDiagram) describes the state of each object participating in the interaction at a certain time in the process of interaction. An object diagram can be seen as an instance of a class diagram at some point.

In UML, object diagrams use the same symbols and relationships as class diagrams, because objects are instances of classes. The following figure shows the model of the object graph. The node can be an object or a class, and the connection represents the relationship between the objects:

2. The difference between class diagram and UML object diagram.

Modeling Technology of UML object Graph

First, modeling the object structure

When modeling the design view of a system, a set of class diagrams can be used to fully describe the abstract semantics and the relationship between them. However, the object structure of the system can not be completely described by using UML object graph. For an individual class, there may be multiple instances, and for a set of classes that are related to each other, there may be quite a number of configurations available between objects. Therefore, when using an object graph, you can only display a set of specific or prototype objects of interest in a certain sense. This is the modeling of the object structure, that is, an object graph shows a set of objects that are related to each other at a certain time.

To model the object structure, follow the following strategies:

(1) identify the modeling mechanism to be used. This mechanism describes the functions and behaviors of some of the systems being modeled, which are generated by the interaction of classes, interfaces, and other elements.

(2) for various mechanisms, identify the classes, interfaces and other elements involved in collaboration, as well as the relationship between these things.

(3) consider the script that runs through this mechanism. Freeze the script at a certain point and report on each object involved in the mechanism.

(4) display the status and attribute values of each object as needed to understand the script.

(5) the chain between objects is displayed to describe the instance of the association between objects.

II. Forward engineering and reverse engineering

1. Forward engineering

The forward engineering of object graph engineering is feasible in theory, but it is limited in practice.

2. Reverse engineering

It is very difficult to reverse engineer the object graph. When debugging a system, it always depends on developers or tools.

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