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UML diagrams

What is UML and what does it contain? Firstly, UML integrates the basic concepts of Booch, OMT and OOSE methods, and most of these basic concepts are the same as those of other object-oriented technologies, so UML must become a simple and consistent modeling language that users of these methods and other methods are willing to adopt. Third, UML is a standard modeling language, not a standard development process. Although the application of UML is necessarily based on the development process of the system, different organizations and application fields require different development processes.

As a modeling language, UML definition includes UML semantics and UML notation.

(1)UML semantics describes precise metamodel definitions based on UML. Metamodel provides a simple, consistent and universal definitional description of all elements of UML in syntax and semantics, enabling developers to achieve consistency in semantics and eliminating the impact of different *** expression methods. UML also supports extended definitions of metamodels.

(2)UML notation defines the notation of UML symbols and provides a standard for developers or development tools to use these graphical symbols and text syntax for system modeling. These graphical symbols and text represent an application-level model that semantically is an instance of the UML metamodel.

The important elements of the standard modeling language UML can be defined by the following five UML diagrams (out of nine):

The *** class is a use case diagram that describes the system function from the user's perspective and indicates the operator of each function.

The second category is static diagrams, including class diagrams, object diagrams, and package diagrams. Class diagrams in UML diagrams describe the static structure of classes in a system. It not only defines the classes in the system, indicating the relationships between classes such as associations, dependencies, aggregations, etc., but also includes the internal structure of classes (class attributes and operations). A class diagram describes a static relationship that is valid throughout the life cycle of the system.

Object diagrams in UML diagrams are instances of class diagrams, using almost exactly the same identity as class diagrams. They differ in that the object graph shows multiple object instances of a class, rather than the actual class. An object diagram is an instance of a class diagram. Because objects have lifecycles, object graphs can exist only for a certain period of time in the system.

A package consists of packages or classes that represent relationships between packages. Package diagrams are used to describe the hierarchical structure of a system.

The third category is Behavior Diagrams. What are UML Behavior Diagrams? Describe the interaction between the dynamic model of the system and its constituent objects. State diagrams in UML diagrams describe all possible states of objects of a class and transition conditions for states when events occur. Generally, state diagrams are complementary to class diagrams. It is not practical to draw state diagrams for all classes, but only for classes that have multiple states whose behavior is affected by the external environment and changes.

Activity diagram describes the activities and constraint relations among activities to satisfy the requirements of use cases, which is helpful to identify parallel activities.

The fourth category is the Interactivity Diagram, which describes the interactions between objects. Sequence diagram in UML diagram shows dynamic cooperation relationship between objects, it emphasizes the order of message sending between objects, and shows interaction between objects; cooperation diagram describes cooperation relationship between objects, cooperation diagram is similar to sequence diagram, showing dynamic cooperation relationship between objects. In addition to showing information exchange, collaboration diagrams also show objects and the relationships between them. If you emphasize time and sequence, use sequence diagrams; if you emphasize hierarchy, choose cooperation diagrams. These two types of graphs are collectively referred to as interactive graphs.

The fifth category is the implementation diagram. What is UMl implementation diagram? Component diagrams describe the physical structure of code components and the dependencies between them. A part may be a resource code part, a binary part, or an executable part. It contains information about the logical or implementation class. Component diagrams help to analyze and understand the extent to which components interact.

Configuration diagrams define the physical architecture of the software and hardware in a system. It can show the actual computers and devices (represented by nodes) and the connections between them, as well as the types of connections and dependencies between parts. Within nodes, executable components and objects are placed to show the correspondence between nodes and executable software units.

From the application point of view, when object-oriented technology is used to design a system, the first step is to describe the requirements; the second step is to establish a static model of the system according to the requirements to construct the structure of the system; the third step is to describe the behavior of the system. Among them, the models established in *** and step 2 are static, including use case diagram, class diagram (including package), object diagram, component diagram and configuration diagram, which are static modeling mechanisms of standard modeling language UML. The model established in step 3 can either be executed or represent the sequential state or interaction relationship when executed. It consists of four graphs: state diagram, activity diagram, sequence diagram and cooperation diagram. It is the dynamic modeling mechanism of UML. Therefore, the main content of UML can also be summarized as static modeling mechanism and dynamic modeling mechanism.

There are two types of modular mechanisms.

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