@startuml

scale 3.0

Object "<u>:Cashier" as C
Object "<u>:Register" as R
Object "<u>:Sale" as S
Object "<u>:SalesLineItem" as SLI  <<collection>>
Object "<u>sl:SalesLineItem" as slSLI
Object "<u>:ProductCatalog" as PC
Object "<u>:ProductSpecification" as PS <<collection>>

C -r- R : > enterItem(itemID, qty)
R -d- PC : > 1: spec := getSpecification(itemID)
PC -d- PS : > 1.1: spec := find(itemID)

R -r- S : > 2: makeLineItem(spec, qty)
S -d- slSLI : > 2.1: create(spec, qty)
S -d- SLI : > 2.2 add(sl)


@enduml