Shulou(Shulou.com)06/02 Report--

This article is to share with you about what UML is. The editor thinks it is very practical, so share it with you as a reference and follow the editor to have a look.

1. Introduction to UML

UMLUML is a well-defined, easy to express, powerful and universally applicable modeling language. It integrates new ideas, new methods and new technologies in the field of software engineering. Its scope is not limited to supporting object-oriented analysis and design, but also supports the whole process of software development starting from requirements analysis.

The development of object-oriented technology and UML can be represented by graphics, and the emergence of standard modeling language is an important achievement. In the United States, as of October 1996, UML has been widely supported by industry, science and technology and application circles. More than 700 companies have expressed support for using UML as a modeling language. By the end of 1996, UML has firmly accounted for 85% of the object-oriented technology market and has become the de facto industry standard for visual modeling languages. On November 17,1997, OMG adopted UML1.1 as a standard modeling language based on object-oriented technology. UML represents the development direction of object-oriented software development technology, and has a huge market prospect, but also has great economic value and national defense value.

UML is a standard graphical representation, it is not object-oriented analysis and design, nor is it a method, it is just a set of symbols.

2. The content of UML

First of all, UML integrates the basic concepts of Booch, OMT and OOSE methods, and most of these basic concepts are the same as those in other object-oriented technologies. Therefore, UML is bound to become a simple and consistent modeling language that users of these and other methods are happy to adopt. Secondly, UML is not only a simple confluence of the above methods, but also widely solicited opinions on the basis of these methods. UML expands the application scope of existing methods. Third, UML is a standard modeling language, not a standard development process. Although the application of UML must be based on the development process of the system, different development processes need to be adopted because of different organizations and different application fields.

As a modeling language, the definition of UML includes two parts: UML semantics and UML representation.

(1) the semantic description of UML is based on the precise metamodel definition of UML. The metamodel provides a simple, consistent and universal definition for all elements of UML in syntax and semantics, enabling developers to be consistent in semantics and eliminating the impact of person-to-person expressions. In addition, UML supports extended definitions of metamodels.

(2) UML notation defines the representation of UML symbols, which provides a standard for developers or development tools to use these graphical symbols and text syntax for system modeling. These graphic symbols and words express the application-level model, and semantically it is an example of the UML metamodel.

The important content of the standard modeling language UML in the UML beginner's guide can be defined by the following five types of diagrams (a total of 9 graphics):

* classes are use case diagrams that describe system functions from the user's point of view and indicate the operators of each function.

The second category is static diagrams (Staticdiagram), including class diagrams, object diagrams, and package diagrams. The class diagram describes the static structure of the class in the system. Not only define the classes in the system, represent the relationships between classes, such as association, dependency, aggregation, etc., but also include the internal structure of the class (class properties and operations). The class diagram describes a static relationship that is valid throughout the life cycle of the system.

An object diagram is an instance of a class diagram, using almost the same identity as the class diagram. The difference between them is that the object graph shows multiple object instances of the class, not the actual class. An object diagram is an instance of a class diagram. Because the object has a life cycle, the object graph can only exist for a certain period of time in the system.

A package consists of packages or classes that represent the relationship between packages. The package diagram is used to describe the hierarchical structure of the system.

The third category is behavior Graph (Behaviordiagram), which describes the dynamic model of the system and the interaction between constituent objects. The state diagram describes all the possible states of the object of the class and the transition conditions of the state when the event occurs. In general, a state diagram is a supplement to a class diagram. In practice, it is not necessary to draw state diagrams for all classes, only for those classes that have multiple states whose behavior is affected by the external environment and changes.

The activity diagram describes the activities to be carried out to meet the requirements of the use case and the constraint relationship between the activities, which is helpful to identify parallel activities.

The fourth category is the interaction diagram (Interactivediagram), which describes the interaction between objects. The sequence diagram shows the dynamic cooperative relationship between objects, which emphasizes the order of messages sent between objects and shows the interaction between objects at the same time; the cooperation diagram describes the cooperative relationship between objects, and the cooperation diagram is similar to the sequence diagram to show the dynamic cooperative relationship between objects. In addition to displaying the exchange of information, the collaboration graph also shows objects and their relationships. If you emphasize time and sequence, use the sequence diagram; if you emphasize the relationship between superiors and subordinates, select the cooperation diagram. These two kinds of graphs are called interactive graphs.

The fifth category is the implementation diagram (Implementationdiagram). The component diagram describes the physical structure of the code components and the dependencies between the components. A part may be a resource code part, a binary part, or an executable part. It contains information about logical classes or implementation classes. Component diagrams help to analyze and understand the degree of interaction between components.

The configuration diagram defines the physical architecture of software and hardware in the system. It can display the actual computers and devices (represented by nodes) and the connections between them, as well as the types of connections and dependencies between components. Within the node, executable components and objects are placed to display the correspondence between the node and the executable software unit.

From the perspective of application, when using object-oriented technology to design the system, the first step is to describe the requirements; secondly, to establish the 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. The models established in the * * step and the second step are static, including use case diagram, class diagram (including package), object diagram, component diagram and configuration diagram, which are the static modeling mechanism of the standard modeling language UML. The model established in the third step can either be executed or represent the timing state or interaction at the time of execution. It includes four graphs: state diagram, activity diagram, sequence diagram and cooperation diagram. It is the dynamic modeling mechanism of the standard modeling language UML. Therefore, the main contents of the standard modeling language UML can also be classified into two categories: static modeling mechanism and dynamic modeling mechanism.

3. The main features of UML

The main features of the standard modeling language UML in the UML beginner's guide can be summed up in three points:

(1) UML unifies the basic concepts of Booch, OMT and OOSE.

(2) UML also draws on the strengths of other schools in the field of object-oriented technology, including the influence of non-OO methods.

The UML symbol representation takes into account the graphical representation of various methods, deletes a large number of symbols that are easily confusing, redundant, and rarely used, and adds some new symbols. Therefore, the ideas of many people in the object-oriented field are imported into UML. These ideas are not invented by UML developers, but are abstracted by developers based on the OO method and rich practical experience in computer science.

(3) UML also put forward some new concepts in the process of evolution.

New concepts such as template (Stereotypes), responsibility (Responsibilities), extension mechanism (Extensibilitymechanisms), thread (Threads), process (Processes), Distribution (Distribution), concurrency (Concurrency), pattern (Patterns), cooperation (Collaborations), activity diagram (Activitydiagram) are added to the UML standard, and the concepts of Type, Class and Instance, Refinement, Interfaces and Components are clearly classified.

Therefore, it can be considered that UML is an advanced and practical standard modeling language, but some of these concepts need to be verified in practice, and there must be an evolutionary process in UML.

4. The application field of UML

The goal of UML in UML beginner's guide is to describe any type of system in the way of object-oriented graph, which has a wide range of applications. Among them, the most commonly used is to establish the model of software system, but it can also be used to describe systems in non-software fields, such as mechanical systems, enterprise organizations or business processes, as well as information systems dealing with complex data, industrial systems or industrial processes with real-time requirements. In a word, UML is a general standard modeling language, which can model any system with static structure and dynamic behavior.

In addition, UML is applicable to different stages of the system development process, from the description of the requirements specifications to the testing after the system is completed. During the requirements analysis phase, use cases can be used to capture user requirements. Through use case modeling, describe the external roles interested in the system and their functional requirements for the system (use cases). The analysis phase is mainly concerned with the main concepts (such as abstractions, classes and objects, etc.) and mechanisms in the problem domain. We need to identify these classes and their relationship with each other, and use UML class diagram to describe them. To implement the use case, classes need to collaborate, which can be described by the UML dynamic model. In the analysis phase, only the objects of the problem domain (real-world concepts) are modeled, without considering the classes that define the technical details of the software system (such as classes that deal with user interface, database, communication, parallelism, etc.). These technical details will be introduced during the design phase, so the design phase provides more detailed specifications for the construction phase.

Programming (construction) is an independent phase whose task is to convert classes from the design phase into actual code in an object-oriented programming language. When building analysis and design models with UML, you should try to avoid considering transforming the model into a specific programming language. Because in the early stage, the model is only a tool to understand and analyze the system structure, thinking about the coding problem too early is not conducive to the establishment of a simple and correct model.

The UML model can also be used as a basis for the testing phase. The system usually needs to go through unit test, integration test, system test and acceptance test. Different test teams use different UML diagrams as the basis for testing: unit testing uses class diagrams and class specifications; integration testing uses component diagrams and collaboration diagrams; system testing uses use case diagrams to verify the behavior of the system; acceptance tests are conducted by users to verify that the results of the system tests meet the requirements determined in the analysis phase.

Thank you for reading! This is the end of this article on "what is UML?". I hope the above content can be of some help to you, so that you can learn more knowledge. if you think the article is good, you can share it for more people to see!

Welcome to subscribe "Shulou Technology Information " to get latest news, interesting things and hot topics in the IT industry, and controls the hottest and latest Internet news, technology news and IT industry trends.