Object-Oriented Software Development with UML - UNU-IIST ...

96 Creating Collaboration Diagramsmsg1():Sale1:s:=size():int:SalesLineItem:Amsg1(0msg2()1:add(e:C)2:delete(e:C):CFigure 7.13: Message to multiobject1*:[for each] sli:=next():SalesLineItemprint():Sale2:print()sli:SalesLineItemFigure 7.14: Performing an operation on each object of a multiobject7.3 Creating Collaboration Diagrams7.3.1 Overview of Design PhaseDuring the design phase, there is a shift in emphasis from application domain concepts toward softwareobjects, and from what toward how. The objects discovered during analysis serve as the skeleton of thedesign, but the designer must choose among different ways to implement them. In particular, the systemoperations identified during the analysis must be assigned to individual objects or classes, these operationsmust be expressed as algorithms. Also, complex operations must be decomposed into simpler internaloperations which are assigned to (or carried out by) further objects.The major task in the design is to create the collaboration diagrams for the system operations identifiedin the requirement analysis phase. The most important and difficult part in the generation of collaborationdiagrams is the assignment of responsibilities to objects. Therefore, the rest of this chapter will mainlydiscuss the general principles for responsibility assignment, which are structured in a format called patterns.The creation of collaboration diagrams is dependent upon the prior creation of the following artifacts:=Conceptual model: from this, the designer may choose to define software classes corresponding toconcepts. Objects of these classes participate in interactions illustrated in the interaction diagrams.System operations contracts: from these, the designer identifies the responsibilities and post-conditions=that the interaction diagrams must fulfill.=Essential (or real) use cases: from these, the designer may glean information about what tasks theinteraction diagrams fulfill, in addition to what is in the contracts (remember that contracts do not sayvery much about the UI-outputs).Report No. 259, July 2002UNU/IIST, P.O. Box 3058, Macau