Coad and Yourdon object-oriented analysis process

The method of Coad and Yourdon is based on information Modeling technology, object-oriented program design and Knowledge Base system, which is divided into object-oriented analysis (OOA) and object-oriented design (OOD). We'll discuss Coad and Yourdon object-oriented analysis here, and then discuss object-oriented design in the next section.

Coad and Yourdon think that object-oriented analysis should mainly consider: an object related to a particular application, the relationship between objects and objects in structure and interaction. In object-oriented analysis, it is necessary to establish an analytic model to describe the function of the system.

OOA's mission.

Object-oriented analysis requires two tasks to be accomplished:

The application problem of formal description is the object that the software system basically constitutes, and the rules and constraints that the system must obey, which is decided by the application environment.

Clearly define how the objects that make up the system work together to accomplish the specified function.

The system model based on object-oriented analysis is based on concept, so it is called conceptual model. The conceptual model consists of a set of related classes. Object-oriented analysis can be built into the system model from top to bottom, and the new class can be constructed gradually from the base of the defined classes.

The order of conceptual model Construction and review is composed of five levels: Class and object layer, attribute layer, service layer, structure layer, subject layer. These five levels do not constitute the level of the software system, but the level of the analysis process, can be said to be different aspects of the problem, each level of work for the system's specifications added a component. When all five levels of work are complete, the task of object-oriented analysis is completed.

Steps for OOA

Object-oriented analysis is usually done in the following steps:

(1). Identifies objects and classes. You can start with the application field and gradually determine the classes and objects that form the basis of the entire application. This step is to identify the classes and objects that are useful to the system by analyzing the responsibility of the target system in the domain and investigating the environment of the system.

(2). Identification structure. The typical structure has two kinds, general--special structure and whole--partial structure. General--a special structure represents a generic class is a base class, a special class is a derived class, a whole--a partial structure represents an aggregation, and is aggregated by a member of a different class into a new class.

(3). Identity attribute. The information that the object holds is called its property. The property of a class describes state information, and the value of the property in an instance of the class represents the state value of the object. For each object, we need to find the attributes that are required for the object in the target system, then arrange the attributes to the appropriate location, find the instance connection, and then check. A description of each attribute should be given, determined by the name of the attribute and the description of the attribute, and specifies what special restrictions exist on the property (such as read-only, attribute-value-limited to a range, and so on).

(4). Identify the service. The action performed by an object when it receives a message is called the service provided by the object, which describes the processing and functionality that the system needs to perform. The purpose of defining a service is to define the behavior of the object and the communication between the objects. The steps include identifying the state of the object, identifying the necessary services, identifying the message connection, and describing the service. You can use graphs similar to flow diagrams to indicate services.

(5). Identifies the subject. It is difficult to grasp the concept model which contains a large number of classes and objects, and the identification theme divides the model, gives the whole frame of the model, and divides the hierarchical structure. But Coad and Yourdon did not offer specific advice on how to identify the subject. When you identify a theme, you can take the topic first, then refine and refine the theme, and then add the topic to the analysis model. The topic is an application-related, rather than an artificially-drawn concept, and the work of the subject layer helps to analyze the results.