Activity diagrams focuses on the sequence of actions.

Ans: First of all, you don’t have to choose.

How do I decide which one is appropriate?.

When do I use a sequence diagram and when do I use an activity diagram?.

Web Interface sends email message Some wait for a response.

Specifically want to leave as an implementation decision.įlat Message Example Heavy border indicates separate process with own control flow.

Used when we don’t want to specify whether or not sender waits for a reponse.

Used when we don’t want the sender to wait for a response Īsynchronous Message Example Roff page 98.

Synchronous Message Example Roff, page 97

Sender waits for response to message before doing anything more.

Used when we want to things to be done one at a time.

Kinds of Messages UML defines four kinds of messages: Sender waits for a reply (Procedural message) The reply to a synchronous message Often not shown Sender does not wait for a reply Don’t know or don’t care Messages Arrows are labeled with the name of the message, or stimulus, that they represent.

When an object is active, either because it is doing something, or because it has sent a message to another object that is doing something on its behalf.

Long narrow vertical box on lifeline indicates focus of control.

Interactions are represented by messages sent from one object to another.

May run entire length of diagram or may start or end within the diagram More notation for names is defined in UML. Lifelines Underline on name indicates object (vs class) Represents time during which the object exists.

Add objects left to right as they get involved.

No significance to position of the active objects on the left to right axis.Starting to look at how the system does something rather that just what is done.Distribute use case behavior to classes.How objects collaborate to realize a use case.Used to model object interactions on a time axis.Sequence Diagrams Blaha and Rumbaugh Sections 7.2 and 8.2

Vending machine sequence diagram