Activity diagram is a type of UML diagram. It shows the control flow of an process starting from the starting point to ending point. It also shows the various decision that appears during the flow of the activity. They are used in business modelling where it shows the dynamic flow of the system. It visually represents the flow of activity in a systematic order.
The main difference between activity diagram and flowchart is that an activity diagram represents the workflow of activities of the system while a flowchart is a graphical steps that shows the sequence of steps to solve a problem.
The different symbols used in activity diagrams are :
Initial State or start
Final State or end
Sequence diagram shows interaction between objects in a sequential manner. It show the order in which the activity takes place in sequence. It show the flow how and in what order the object flow in system flow.
The main difference between sequence diagram and activity diagram is that sequence diagram is used to represent the time order of a system flow whereas in activity diagram it shows the execution of the flow.
Different symbols used in sequence diagram are: