UML学习-sequesce diagram

Combined Fragments

• Alternative fragment (denoted “alt”) models if…then…else constructs. 二选一
• Option fragment (denoted “opt”) models switch constructs. 多选
• Break fragment models an alternative sequence of events that is processed instead of the whole of the rest of the diagram.
• Parallel fragment (denoted “par”) models concurrent processing. 并行分支
• Weak sequencing fragment (denoted “seq”) encloses a number of sequences for which all the messages must be processed in a preceding segment before the following segment can start, but which does not impose any sequencing within a segment on messages that don’t share a lifeline.
• Strict sequencing fragment (denoted “strict”) encloses a series of messages which must be processed in the given order.
• Negative fragment (denoted “neg”) encloses an invalid series of messages.
• Critical fragment encloses a critical section.
• Ignore fragment declares a message or message to be of no interest if it appears in the current context.
• Consider fragment is in effect the opposite of the ignore fragment: any message not included in the consider fragment should be ignored.
• Assertion fragment (denoted “assert”) designates that any sequence not shown as an operand of the assertion is invalid.
• Loop fragment encloses a series of messages which are repeated. 循环

下表列出了常用的组合片段：

        有关如何解释序列的片段

        默认情况下，序列图表明可能发生的一系列消息。 在运行的系统中，可能会出现您未选择显示在关系图上的其他消息。

        以下片段类型可用于更改此释义：