Use Case Diagram

Definition of Use Case

Use case is the circuit/description of a group of inter-related and form a system of regularly conducted or supervised by an actor. Use case are used to establish behavior of objects/things in a model and in Realized by a collaboration. General use case is described by an ellipse with a solid line. Usually containing nama. Use case describes the process of the system (system requirements from the user perspective).

In general use case is :

·         - The pattern of behavior of the system

·         - A sequence of related transactions performed by an actor

Use case diagram consist of :

- Use case 
- Actors

·        - Relationship

·        - System boundary boxes (optional)

·        - Packages (optional)

Definition of Activity Diagram

Activity diagrams describe the flow of activity in the system that is being designed, how each flow begins, a decision that might occur, and how they ended. Activity diagrams can also illustrate the parallel processes that may occur in some execution. Activity diagram is a special state diagram, where most of the action and the state is mostly triggered by a transition at the completion of the previous state (internal processing). Therefore the activity diagram does not describe the internal behavior of a system (and the interaction between the subsystems) is exact, but rather describes the processes and pathways of activity above the general level. Describe business processes and sequence of activities in a process. Used in business modeling to show the sequence of activities of a business process. The structure is similar to a flowchart or diagram Data Flow Diagram in structured design. Very useful if we make this first diagram in modeling a process to help understand the overall process. Activity diagram is based on one or more use cases in use case diagrams.

Definition Of Sequence diagrams

Sequence diagram (sequence diagram) is a diagram which shows or displays the interactions between objects in the system are arranged in a sequence or time series. The interactions between objects including users, displays, and so on in the form of message. Sequence Diagram is used to describe a scenario or series of steps carried out as a response to an incident / event to produce a certain output. Sequence Diagram beginning of what had triggered the event, the process and what changes are happening internally and what the resulting output.

This diagram is specifically associated with the use case diagram. Sequence diagram also shows step by step what should happen to produce something within the use case. Sequence diagrams can also change the attributes of the class or extending methods that have been established by the class diagram, even creating a new class. Sequence diagrams model the flow of logic within a system in a visual manner.

Sequence diagrams are usually used for the purpose of analysis and design, focusing on the identification method in a system . Sequence diagrams are usually used for modeling :

    - Description of the existing system in a some use case in the use case diagram, which describes the relationship between actor and use case diagrams.

·         - The logic of the method (operation, function or procedure).

      - Logic of service (high- level method).

Use Case diagrams ( ex : The blogger ) 

          Use case models capture functional information about systems (as-is or to-be). They describe how systems interact with the environment as well as the kind of tasks 'actors' perform using the system. Use case models consist of use case diagrams and use case specifications. The latter describe specific user scenarios.

In an attempt to illustrate how use case modelling is used in systems analysis I will provide the main use cases for blogger as well as a use case specification for the 'Create Personal Profile' use case. 

Identifying the main Actors

      In UML (Unified Modelling Language) an Actor is defined as anything that communicates with the system and is external to it. Hence, it could involve end users, external devices that interact with the system or other subsystems.

The first step in creating use case diagrams is to identify the main Actors. To find the main Actors we need to answer the following questions:

·         Who interacts with the system?

·         Who or What executes the use cases?

·         Who and What runs the functions of the system? 

·         Who uses or will be using the system?

In blogger, two obvious Actors are Users and Admin. Users want to use the system to connect with others while Admin use the system to create pages and promote their services.

Once we identify the main actors we need to find the main use cases.

Identifying the main use cases 

To identify the main use cases we answer the following questions:

·         What are the main goals of Actors?

·         What are they (Actors) trying to achieve?

·         What tasks will they be doing?

Pay special attention to CRUD operations. Do actors need to create, read, update or delete data from the system? In certain situations, especially when business requirements and specifications are written down, textual analysis may help in identifying use cases. 

In the above sentence, phrases in bold are use case suspects. Furthermore, we conclude to the following main use cases :

1. Manage Profile : Describes how a user creates a personal profile.
2. Manage Posting : Describes how users add posting to their personal profile page.
3. Manage Comment : Describes how users add comment to their personal profile page.
4. Template : Describes how users add template to their personal profile page.
5. Follow Blog : Describes how a user connects with other users' personal profile pages.
6. Email or password wrong : Describes how admin connect with users.