Sequence Diagram

•Objects are represented horizontally across the top of the diagram

•The first object is an Actor, the one who initiated the Use Case

•Each object has a lifeline

•some exist before and after the Use Case

•some are created during the Use Case

•some are destroyed during the Use Case

•An active object is indicated by a narrow rectangle

•(on the activation stack)

•Time is represented vertically down the diagram. Time moves forward as you go downwards

Figure 15.2 Sequence Diagram

Figure 15.4 Sequence diagram

Figure 15.17 Focus of control

Figure 15.18 Showing returns

Figure 15.19 Message to ‘this’

Figure 15.21 Destroying an object

Figure 15.22 Conditional message

Figure 15.23 Mutually exclusive conditional messages

Figure 15.24 Iteration

Figure 15.25 Iteration over a sequence of messages

Figure 15.26 Iteration over a multiobject

Figure 15.27 Messages to a class itself, not an object

Sequence Diagram - example

Check to see if there is enough quantity on hand

If there is, then remove that quantity from inventory and create a delivery item for those goods

If there is not enough on hand, then create a back order line item

We have 4 objects: an orderLine, product, delivery line item, and a back order line item.

The delivery line item and back order line item will be created during the scenario

Sequence Diagram - example

:OLine :Product

1:hasStock:=checkQOH()

2:[hasStock]remove()

:DelItem3:[hasStock]new()

:BOItem

4:[not hasStock]new()

Message numbers are not necessary on SD, and are not shown in the text.

Sequence Diagram - example 2

Check the quantity on hand

if there is adequate stock, then check for the need to reorder

if we need to reorder then create a reorder line item

Sequence Diagram - example 2

:OLine :Product

1:hasStock:=checkQOH()

2:[hasStock] remove()

:RItem

2.1:needToReorder:=checkLevel()

2.3:[needToReorder] new()

Sequence Diagram - example 3

For each line of a purchase order

check the quantity on hand

if there is enough, remove the quantity from inventory

Sequence Diagram - example 3

:OLine :Product

1.1:hasStock:=checkQOH()

1.2:[hasStock] remove()

:PO

1:*[for each line] checkQOH()

Sequence Diagram Example

Consider the sequence of events:

For each line of a purchase order

Check the quantity on hand

If there is enough,

remove that quantity from inventory

create a delivery item for those goods

check for the need to reorder

if we need to reorder then create a reorder line item

If there is not enough on hand, then create a back order line item

As a Sequence Diagram

:OLine :Product

hasStock:=checkQOH()

[hasStock] remove()

:PO

*[for each line] checkQOH()

:DelItem

:BOItem

[hasStock] new()

[not hasStock] new()

:RItem

needToReorder := checkLevel()

[needToReorder] new()

As a Collaboration Diagram

128937:POrder

:OLine

:DelItem {new}

1*[for all order lines] checkQOH()

1.1: hasStock:=checkQOH()1.2: [hasStock] remove()

1.2.1: needToReorder := checkLevel()

1.2.2:[needToReorder] new()1.3a:[hasStock] new()

:Product

:RItem {new}1.3b: [not hasStock] new()

:BOItem {new}