Group 2 work What is sequence diagram ? What is sequence diagram ? Why do we use it ? Why do we use it ? What is basic notation of SD? What is basic notation of SD? diagrams exploration diagrams exploration Group members: Edgaras, Ronaldas, Julius and Andrius

What is Sequence diagrams? A sequence diagram (SD) is a picture that shows, for one particular scenario of a use case, the events that external actors generate their order, and inter- system events. A sequence diagram (SD) is a picture that shows, for one particular scenario of a use case, the events that external actors generate their order, and inter- system events. Also SD is an interaction diagram that details how operations are carried out, what messages are sent. Also SD is an interaction diagram that details how operations are carried out, what messages are sent.

What is Sequence diagrams? SD are organized according to time. SD are organized according to time. The time progresses as you go down the page. The time progresses as you go down the page. The objects involved in the operation are listed from left to right according to when they take part in the message sequence. The objects involved in the operation are listed from left to right according to when they take part in the message sequence.

Why do we use SD? Because we have to design the software to handle these events (from the mouse, keyboard, another system, …) and execute a response. Basically a software system reacts the three things: Because we have to design the software to handle these events (from the mouse, keyboard, another system, …) and execute a response. Basically a software system reacts the three things: 1) External events from actors (humans or computers). 1) External events from actors (humans or computers). For example, when a cashier enters an item’s Id, the cashier is requesting the POS system to record that item’s sale (The enterItem event). That event initiates an operation upon the system. The use case text implies the enterItem event, and the SSD makes it concrete and explicit. For example, when a cashier enters an item’s Id, the cashier is requesting the POS system to record that item’s sale (The enterItem event). That event initiates an operation upon the system. The use case text implies the enterItem event, and the SSD makes it concrete and explicit. 2) Timer events. 2) Timer events. 3) Faults or exceptions (which are often from external sources). 3) Faults or exceptions (which are often from external sources).

What is the basic notation of sequence diagrams? A sequence diagram depicts the sequence of actions that accrue in a system. The invocation methods in each object, and the order in which the invocation accurse is captured in a SD. This makes the SD a very useful tool to easily represent the dynamic behavior of the system. A sequence diagram depicts the sequence of actions that accrue in a system. The invocation methods in each object, and the order in which the invocation accurse is captured in a SD. This makes the SD a very useful tool to easily represent the dynamic behavior of the system. A SD is two – dimensional in nature. An the horizontal axis, it show life of the object that it represents while on the vertical axis it shows the System of the creation or invocation of these objects. A SD is two – dimensional in nature. An the horizontal axis, it show life of the object that it represents while on the vertical axis it shows the System of the creation or invocation of these objects. Because it uses class name and object reference the SD is very useful in elaboration and detailing the dynamic design and the sequence and origin of invocation of objects. The SD is one of most widely used dynamic diagrams. Because it uses class name and object reference the SD is very useful in elaboration and detailing the dynamic design and the sequence and origin of invocation of objects. The SD is one of most widely used dynamic diagrams.

15.7 diagram Life line boxes and life lines and messages. Situation : Register and sale. Diagram shows how register and sale classes change they information

Diagram 15.8 Diagram shows 2 ways a return result from a message. Diagram shows 2 ways a return result from a message.

Diagram 15.9 This diagram shows message being sent from an object to itself by using a nested activation bar This diagram shows message being sent from an object to itself by using a nested activation bar