Lifeline: Lifelines are vertical dotted lines that indicate the object's activity over time. Lifeline is a named element that represents an individual participant in the connection. While parts and structural properties may have multiplicity, lifelines represent only one interconnected entity.

生命線 ：生命線是垂直虛線，指示對象隨時間的活動。 生命線是一個命名元素，代表連接中的單個參與者。 盡管零件和結構特性可能有多種多樣，但生命線僅代表一個相互聯系的實體。

Messages: Messages are nothing but the arrows that represent calls between objects. Half-arrowed lines are used to represent asynchronous messages. Asynchronous messages are sent from an object that will not wait for a reply from the receiver before continuing its tasks.

消息 ：消息不過是代表對象之間調用的箭頭而已。 半箭頭線用于表示異步消息。 異步消息是從對象發送的，該對象在繼續執行任務之前不會等待接收者的答復。

Execution Occurrence: Execution boxes present the time an object needs to complete a task. When an object is busy executing a process or waiting for a reply message, use a thin gray rectangle placed vertically on its lifeline.

執行發生 ：執行框顯示對象完成任務所需的時間。 當對象忙于執行過程或等待回復消息時，請使用垂直放置在其生命線上的細灰色矩形。

Interaction Fragment: It is the named element that represents the most general interaction segment. Example of Interaction Fragment:

交互片段 ：這是表示最一般的交互片段的命名元素。 交互片段示例：

• Occurrence
• Execution
• Interaction use

Synchronous Message: It requires a response before the interaction can proceed. It's usually drawn using a line with a solid arrowhead pointing from one object to another.

同步消息 ：在進行交互之前，需要響應。 通常使用帶有實心箭頭的線繪制，該線從一個對象指向另一個對象。

Asynchronous Message: It does not require a response before the interaction can proceed. It is usually drawn using an arrow.

異步消息 ：在交互可以繼續之前，不需要響應。 通常使用箭頭繪制。

Reply Message: It is drawn by the dotted arrow moving backward to the original message.

回復消息 ：由虛線箭頭向后移動到原始消息。

Self Message: A message sent to itself and it is represented by the U shaped arrow.

自我信息 ：發送給自己的信息，用U形箭頭表示。

Found Message: A message sent from an unknown beneficiary, shown by an arrow from an endpoint to a lifeline.

找到的消息 ：從未知受益人發送的消息，由從端點到生命線的箭頭顯示。

Lost Message: A message sent to an unknown beneficiary. It's shown by an arrow going from a lifeline to an endpoint, a filled circle or a cross(x).

丟失的消息 ：發送給未知受益人的消息。 它由從生命線到終點的箭頭，實心圓或十字(x)表示。