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This article mainly introduces the basic concept of UML, has a certain reference value, interested friends can refer to, I hope you can learn a lot after reading this article, the following let the editor take you to understand it.

Basic Concepts of easy introduction to Unified Modeling language UML

Composers will compose the melodies in their heads into music, architects will draw blueprints for the buildings they design, and these music and blueprints are Model, and the process of constructing these models is called Modeling. Software development, like music composition and architectural design, must present the ideas and results of various workflows such as requirements, analysis, design, implementation, deployment and so on, which is the modeling of software system.

So why model? The classic answer is: the difference between building a building and building a kennel is that you don't need a design to build a kennel. To produce qualified software, you need a set of specifications about architecture, processes, and tools.

The current * version of UML officially released by OMG is 2.0 and can be downloaded from http://www.uml.org/.

UML consists of graphs and metamodels. Graphs are syntax and metamodels are semantics. UML mainly consists of three basic building blocks: Things, Relationships and Diagrams. In this series, we will introduce these basic components of UML and UML tools and applications, so that readers can form a preliminary overall impression of UML. In the following series, several examples are used to gradually unfold these contents.

Basic building blocks of 1.1UML

1.1.1 things

Things are the final result of entity abstraction and the basic members of the model. UML includes structural things, behavioral things, grouped things and annotated things.

(1) structural things (Structuralthings)

Structural things are the static parts of the model, which are used to present the representation elements of concepts or entities. They are the most common elements in software modeling. There are seven kinds of them:

Class: a class is a collection of objects that have the same properties, methods, relationships, and semantics

Interface (Interface): an interface refers to the services (operations) provided by a class or component, describing the visible actions of the class or component

Collaboration: collaboration describes a set of classes and their associated collections that collaborate to accomplish a particular task, which are used to model the implementation of a use case

Use case (UseCase): a use case defines a business goal achieved by the interaction between the executor (the person who interacts with the system outside the system) and the system being considered.

Active class (ActiveClass): the object of the active class has one or more processes or threads. An active class is very similar to a class, except that the behavior of the element represented by its object exists at the same time as other elements.

Component: a component is a physical, replaceable part that contains a collection of interfaces, such as COM+, JAVABEANS, etc.

Node: a node is a physical element that exists when the system is running, representing a computable resource, which usually takes up some memory and has processing power.

(2) behavior things (Behavioralthings)

Behavior thing refers to the dynamic part of the UML model, which represents the "verb" in the sentence and represents the part of the model that changes with time and space. It includes two categories:

Ineraction: an interaction consists of a series of messages exchanged between a group of objects in a specific context to achieve a specific purpose.

State machine (statemachine): a state machine consists of the states of a series of objects.

(3) grouped things (Groupingthings)

You can think of grouped things as a "box" in which the model can be decomposed. At present, there is only one grouped thing, namely package. Structural things, action things, and even grouped things can all be put in a package. Packages are purely conceptual and exist only in the development phase, while components exist at run time.

(4) annotate things (Annotationalthings)

Annotated things are the explanatory part of the UML model.

1.1.2 relationship

Relationships are the way things are connected, and four relationships are defined in UML:

(1) Dependencies: the semantic relationship between two things, in which a change in one thing affects the semantics of the other.

(2) Association: a structural relationship that describes the connection between a group of objects, such as aggregation (describes the structural relationship between the whole and the parts)

(3) Generalization: a generalization-specialization relationship

(4) Realization: the semantic relationship between classes in which one class specifies a contract guaranteed by the other class.

1.1.3 figure

A graph is a classification of a collection of things, and UML contains a variety of graphs:

(1) Class diagram (ClassDiagram): class diagram describes the classes contained in the system, the internal structure of classes and the relationship between classes.

(2) ObjectDiagram: an object diagram is a concrete example of a class diagram

(3) PackageDiagram: the package diagram shows the package and the dependency class diagram between them.

(4) component diagram (CompomentDiagram, also known as component diagram): component diagram describes the physical structure of code components and the dependencies between them.

(5) deployment diagram (DeploymentDiagram): deployment diagram defines the physical architecture of software and hardware in the system.

(6) use case diagram (UsecaseDiagram): from the user's point of view, the use case diagram describes the functions and requirements of the system, and shows the relationship between various roles outside the system and various use cases within the system.

(7) sequence diagrams (SequenceDiagram): sequence diagrams represent dynamic cooperative relationships between objects.

(8) collaboration diagram (CollaborationDiagram): cooperation diagram describes the cooperative relationship between objects.

(9) State diagrams (StatechartDiagram): state diagrams describe all possible states of a class of objects and the transition conditions of states when events occur.

(10) activity diagrams (ActivityDiagram): activity diagrams describe the execution sequence of various activities in the system. This is the end of this section on UML.

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