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UML practices-UML use case diagrams and activity diagrams

The key to dealing with object-oriented problems is modeling. Modeling can abstract many important details in a complex world. Many modeling tools encapsulate UML (that is, UnifiedModelingLanguage ™), and the purpose of this course is to demonstrate the highlights of UML.

There are nine modeling icons in UML, namely:

Use case diagram

Class diagram

Object graph

Sequence diagram

Collaboration diagram

State diagram

Activity diagram

Component diagram

Configuration diagram

Some parts of this course contain page links to the details of these diagrams. And each part has a small problem, test your understanding of this part.

Why is UML important?

To answer this question, let's look at the construction industry. The designer designed the house. The builders used this design to build the house. The more complex the building, the more important the communication between designers and builders. Blueprints have become a required course for designers and builders in this industry. Writing software is like building a building. The more complex the system, the more important the communication between the people involved in writing and configuring the software. Over the past decade, UML has been the "architectural blueprint" between analysts, designers and programmers. Now it has become part of the software industry. UML provides a common language for analysts, designers and programmers in software design.

UML practice is applied to solve object-oriented problems. If you want to learn UML, you must be familiar with the fundamental principles of object-oriented problem solving-- all starting with the construction of models. A model model is the abstraction of the fundamental problem. The domain domain is the real world in which the problem lies.

The model is composed of object objects, which interacts with each other by sending messages messages to each other. Remember to think of an object as "alive". Objects have what they know (property attributes) and what they can do (behavior or action behaviorsoroperations). The value of the object's property determines its state state.

The class Classes is the "blueprint" of the object. A class encapsulates attributes (data) and behaviors (methods or functions) in a separate entity. The object is an instance of the class instances.

Use case diagram

The use case diagram Usecasediagrams in UML practice describes the impression of the system from the perspective of an external observer. Emphasize what the system is rather than how the system works.

The use case diagram is closely related to the plot. Plot scenario refers to what happens when someone interacts with the system. The following is the plot of a hospital outpatient department.

"A patient called the outpatient department to make an appointment for an annual physical checkup. The receptionist found out the nearest unbooked time in the appointment log book and wrote down the appointment record for that time."

A use case Usecase is the sum of a series of scenarios that complete a job or achieve a goal. The role actor is the person or event that initiates an event related to the job. The role simply plays the role of a person or object. The figure below is an outpatient MakeAppointment use case. The character is a patient. The link between the role and the use case is the communication contact communicationassociation (or communication communication for short)

The character is a human icon, the use case is an ellipse, and the communication is the line that connects the character to the use case.

A use case diagram is a collection of roles, use cases, and relationships between them. We have made MakeAppointment part of a diagram with four roles and four use cases. Note that a single use case can have multiple roles.

Use case diagrams are useful in three areas in UML practice.

Determine characteristics (requirements). When the system has been analyzed and designed, new use cases generate new requirements

Customer newsletter. Using use case diagrams can easily show the relationship between developers and customers.

Generate test cases. The plot of a use case may produce a batch of test cases for these scenarios.

Activity diagram

The activity diagram in UML practice activitydiagram is a very special flow chart. There is a relationship between the activity diagram and the state diagram. The state diagram focuses on the objects in the process, while the activity diagram focuses on a separate process action flow. The activity diagram tells us about the dependencies between activities.

For our example, we use the following process: "withdraw money through ATM."

This activity has three classes Customer,ATM and Bank. The whole process starts with a black circle and ends with a black-and-white concentric circle. The activity is represented by a rounded rectangle.

Activity diagrams can be decomposed into many objects swimming lane swimlanes, which can determine which objects are responsible for which activities. Each activity has a separate transfer transition to connect to these other activities.

Transfer may branch branch into more than two mutually exclusive transfers. The guard expression (in []) indicates that the transfer is derived from a branch. The branch and the merged merge at the end of the branch are represented by a diamond in the figure.

The transfer can also break down the fork into more than two parallel activities. The thread at the end of the decomposition and the end of the decomposition, combined with join, are represented by bold lines in the diagram.

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