I am hard to understand the association class, and I feel some problems here. Below is the article or article disconnected by I extracted.
The first is the basic definition of the associated class:
Associated class associations may be recorded, which can be recorded in an associated class. Figure 3 is an associated class in which the associated class is introduced on the basis of FIG. The association class is connected to the associated connection. Figure 4 is another method of achieving the above objective, that is, enabling the employment relationship into a formal class.
Below is a statement of Babituo from the UML discussion group.
Understanding from the level of understanding
Since we have a common philosophical hobby, I think this question first finds an answer from the philosophy level will be more beneficial to us to understand it. We talk from the ER chart and class association map. The starting point of the error of the ER map is from the perspective of the information system main body, the purpose is to obtain the results of the real world from the information angle decomposition. It focuses on how to directly use data relationships to translate the relationship between real world real things. Because the ER model is a direct data relationship model, since the ER chart seems to be static, dynamic things should be static, just like the use of linearization methods to handle nonlinear issues. As a "class-associated" map for one of the object-oriented static model, the starting point of understanding the problem is a living thing in the real world. The purpose is to first understand the law of reality the changes in the move of the real world, and consider how to computer This nature of this essential law is simulated. Class - related maps are called static models because it reflects the relative stability of the relationship between things itself and things, this stability is discrete samples through the change process of things, and then analyzes discovery The relatively constant portion. Our purposes are not to get this relatively stable object and object relationship model, but based on this part of the understanding, re-fitting the new real world process model, the new process has a computer participation. Previously, since the answer had not been found in the technical standard, the answer to the object and object relationship information has not yet found the answer to the object and object relationship information, so it is necessary to save this information with the relational database, so the two models are mixed. This causes the mutual interference of the two ideas. Today, XML has become a standard of persistent storage and exchange of distributed objects and object relationship information, but the platform tool level has not yet mature OO databases, so this footprint will still harass us, we It must be clearly recognized that this is just a technical means, not ideas. We tried to get an object-oriented static model and an entity relationship model for the object-oriented method to get ER, at least in thought, although there is a form of format. Looking for the method of associated classes should be from a purely object-oriented mode. We initially establish object-oriented static models, there are two points: 1. All things must have objects to complete; 2. All objects must do appropriate things. By the way, the following is true: these two principles are actually the principle of enterprise management, so I said that now the company's management thinking is still in the structured era, it is an object-oriented era. The so-called association, just when the object is doing, the pipeline relationship between communication between different objects. When you find that some of these pipeline relationships are complicated, you need to maintain, and you can get to a separate responsibilities, you think that if there is an object to deal with these relationships, you can define an associated class. When you start thinking about all use cases, you don't need to consider the existence of associated classes. As long as you meet the above two principles, as you have achieved, you need to combine the object models implemented by each use case. It is a total object model that your overall object is more and more complicated. At this time, you can consider using high-level means such as associated classes, abstract classes. At this time, it is necessary to ensure the total use case model and the consistency implementation of each use case.
