Sender of the message must wait for the receiver to process the message before continuing to send another message. Used to contain additional useful information for the modeller/developer. The length of the bar represents the duration of an object’s activeness.Įnds the lifeline of objects or messages.Ĭan be a human user or other external subjects. Represents an active object during an interaction between two objects. Two or more message sequences exist, and a choice must be made between the two of them.Ī sequence can only occur under certain circumstances. Objects or parts of a system that interact during the sequence. Now that we have discussed what it is and its purpose, let’s take a look at some commonly used symbols and components in a sequence diagram. This documentation can be passed on to other persons or organizations. To be used as a handy form of documentation on how a system functions. To show the time order in which events occur. To illustrate interactions between actors (system users) and the system, or various parts of a system. So when should sequence diagrams be used, and what can they be used for?
SEQUENCE DIAGRAM EXAMPLE SIMPLE SOFTWARE
They are most commonly used by software developers but have been increasingly adopted within business settings as well, due to its ability to show how a system operates clearly.
Such diagrams typically illustrate how different parts of a system interact with each other, and in what order, to achieve an outcome.
For example, an employee is dependent on the organization.Sequence diagrams are commonly used by developers to depict interactions between objects in a use case (actions that show interactions between an actor and a system to achieve a goal). Change in one class will create change in another class.
For example, if an organization closes, all employees will have to leave.ĭependency shows that one class depends on another. In composition, a class is strongly connected to another class that it will stop functioning without it. The aggregation has another special type, called composition. For example, if an employee does not come, the organization will remain there. In aggregation, 2 classes have a whole-part relationship. If 100 people work at an organization, then the attribute has multiplied 100 times. The multiplicity factor in association represents how many times an attribute is multiplied. The association between a student and school is “studies”. Checking, Savings, and Credit Accounts are generalized by AccountĪssociation shows a static relationship between two entities. The class diagram allows a subclass to inherit from multiple superclasses but it can’t be used to model interface implementation. Generalizations are often known as Inheritance because it links a subclass to its superclass. There are three main types of relationships here: To create a class diagram, the next step is building relationships. You don’t need to show operations that are similar to attributes because one can already deduce that from the information. They correspond to the methods of a class. Operations are processes that a class knows to carry out. Attributes must be meaningful and are usually used with the visibility factor that describes the accessibility of an attribute. You can simply add new attributes or derive new attributes from already listed attributes. Moreover, an abstract class should be written in italics.Īttributes are written in the middle compartment and list down all the properties of the object being modeled. It should be written in bold in the top compartment and start with a capital letter. The class name is important for graphical representation. The rectangle is divided into three compartments with the topmost being Class Name, then Attributes in the middle, and Operations in the bottom. There are three major parts of a class diagram as shown in the image below:Ī single rectangle is used to represent the class as shown above.
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