If condition sequence diagram3/29/2024 Notes can be included in any kind of UML diagram. The diagram has a clarifying note, which is text inside a dog-eared rectangle. The expression in square brackets,, is a condition. The asterisk on the self call means iteration (to make sure there is available room for each day of the stay in the hotel). If so, then the Hotel creates a Reservation and a Confirmation. In this diagram, the Hotel issues a self call to determine if a room is available. The activation bar represents the duration of execution of the message. The alternative combined fragment is utilized in a sequence diagram to define a section of a cluster of lifelines/actors, representing conditional flow. An arrow goes from the sender to the top of the activation bar of the message on the receiver's lifeline. If the Hotel has available rooms, then it makes a Reservation and a Confirmation.Įach vertical dotted line is a lifeline, representing the time that an object exists. The HotelChain then sends a makeReservation() message to a Hotel. The UserInterface sends a makeReservation() message to a HotelChain. The object initiating the sequence of messages is a Reservation window (the UserInterface). The objects involved in the operation are listed from left to right according to when they take part in the message sequence.įollowing is a Sequence Diagram for making a hotel reservation. The time progresses as you go down the page. Sequence diagrams are organized according to time. In contrast, interaction diagrams are dynamic, describing how objects collaborate.Ī sequence diagram is an interaction diagram that details how operations are carried out: what messages are sent and when. UML sequence diagrams are used to show how objects interact in a given situation.Class diagrams are static model views. Lower equals Later).Ī popular use for them is to document the dynamics in an object-oriented system.Īn important characteristic of a sequence diagram is that time passes from top to bottom : the interaction starts near the top of the diagram and ends at the bottom (i.e. The UML sequence diagram gallery contains many examples, but here's a typical sequence diagram based on a system use case scenario : For each key collaboration, diagrams are created that show how objects interact in various representative scenarios for that collaboration. You can use the If else condition, also called alternatives in UML terms. The diagram above shows how objects interact in the "rent item" collaboration when the item is not available during the requested period. 1.Is there a standard way to show a conditional sequence Yes. Note that this highlight is not part of the diagram itself.Īs with all UML diagrams, comments are shown in a rectangle with a folded-over corner : To clarify how execution switches from one object to another, a blue highlight was added to represent the flow of control. To relate the comment to whatever diagram elements it is about, connect them with dashed lines. Objects as well as classes can be targets on a sequence diagram, which means that messages can be sent to them. A target is displayed as a rectangle with some text in it. Below the target, its lifeline extends for as long as the target exists. The lifeline is displayed as a vertical dashed line. Where 'name' is the name of the object in the context of the diagram and 'Type' indicates the type of which the object is an instance. For example, the following code activates the server with a login call: C->S: Login (Username, Password) activate S. Note that the object doesn't have to be a direct instance of Type, a type of which it is an indirect instance is possible too. Mermaid.js sequence diagrams allow you to skip the activate and deactivate lines to keep your diagrams condensed by adding a + and - syntax to messages. So 'Type' can be an abstract type as well.īoth name and type are optional, but at least one of them should be present. Some example :Īs with any UML-element, you can add a stereotype to a target. There are other anonymous objects of the same type and giving them names is the only way to differentiate them.You want to refer to it during the interaction as a message parameter or return value.They can be displayed with icons as well :Īn object should be named only if at least one of the following applies Some often used stereotypes for objects are «actor», «boundary», «control», «entity» and «database». Try to avoid long but non-descriptive names when you're also specifying the type of the object (e.g.
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