Computer science: sequence diagrams

Self-tutoring about software modeling: the tutor mentions sequence diagrams.

Sequence diagrams show the communication among objects within a system. Typically the activity starts from top left: the time axis is downward, while the “object axis” reaches rightward.

Objects are represented by vertical bars; signals tend to move to the right, from object to object. Replies can go back from right to left.

Sequence diagrams are valued among system designers as being a key type of model if one wants to build a system.

Source:

Sommerville, Ian. Software Engineering, tenth edition. Toronto: Pearson, 2016.

Jack of Oracle Tutoring by Jack and Diane, Campbell River, BC.