Show object creation (from DAL) in UML sequence chart

Question

I have 3 classes: Controller, DAL and Entity. The controller calls the DAL requesting an Entity. The DAL retrieves the entity data from the DB and creates a new Entity class which is then returned to the Controller. How do I show this on a UML sequece chart (no need to show the DB)?

2nd question: how should we share UML diagrams on SO? :)

Thanks in advance

Answer 1

   Controller       DAL               DB
        |            |                 |
        | get entity |                 |
        |----------->| get entity data |
        |            |---------------->|
        |            |< - - - - - - - -|
        |            |                 |
        |            |--               |
        |            |  |create entity |
        |            |<-               |
        |<- - - - - -|                 |

note: "Create entity" is a "self-message", so it starts from DAL's lifeline and goes back into DAL's lifeline. I just can't draw it better with characters. Forward messages are continous line, reply messages are dashed line.

EDIT: reflecting on comment, you can also show Entity's lifeline, if it's important.

   Controller       DAL               DB
        |            |                 |
        | get entity |                 |
        |----------->| get entity data |
        |            |---------------->|
        |            |< - - - - - - - -|
        |            |                 |
        |   entity   |---->Entity      |
        |<- - - - - -|       |         |
        |            |       |         |

It's useful if you want to show other calls to Entity as well.