Message (Instance Creation)   An instance creation is used if an instance needs to be created during the lifetime represented by the diagram. Many of the instances are assumed to be in existence when the diagram lifetime starts, those that aren't need to be created. Created instances typically appear at a point on the diagram offset from the other instances. When time is represented by the vertical axis they appear lower than the other instances.

Explanation

Typically many of the participants that are involved in the interaction are positioned near an edge of the diagram and have a lifeline that continues through the lifetime of the whole diagram. Some participant however are created during the lifetime represented by the diagram, these need to be explicitly created and the participants begin their life at the appropriate point in the diagram offset from the other "older" instances.

Related Entries

Stop  Paired Element An Instance destruction is related to an instance creation as a paired element. An instance can be destroyed during the lifetime of the sequence diagram. It may have been created by a previous message or have been in existence at the time the diagram's lifetime began. It is quite common to create an instance to use its services and then to destroy it again.

Lifeline  Used Together An instance lifeline is related to an instance creation in the sense that as soon as an instance is created its lifeline is represented by a dotted line that continues until the instance is destroyed or until the end of the lifetime represented by the diagram.