Control Flow Design

Question 1

What are the strong points of using use cases?

Answer 1

• Provide a good structtured description of what a system must achieve
• Good for specifiying actor interfaces
• Ideal for incrementally collecting requirements
• Good when initial requirements are poorly understood

Question 2

What are the weak points of using use cases?

Answer 2

• Can only describe business functions; not higher or lower level things
• Cannot model hierarchical control strucutre of a software system
• Control logic is only implicit

Question 3

What are the 2 main stlyes of modelling behaviour?

Answer 3

Flow-based model; actions chosen in a predetermined order

State-based model; actions triggered when in certain states

Question 4

What are 2 Properties of guards?

Answer 4

Mutually exclusive

Exhaustive

Question 5

What are the strong points of composing diagrams of subdiagrams?

Answer 5

• Can split complex control flows
• Each subdiagram has a logical entry/exit
• Can capture different levels of detail

Question 6

What are the weak points of composing diagrams of subdiagrams?

Answer 6

• Can’t distinguish between exit wih success from exit with failure
• NEed to invent state variables to control what happens at higher levels

Question 7

What are swim lanes used for in a UML activity diagram?

Answer 7

Show that different activities are done by different business departments
Can also show multithreaded processes executed on different hardware

Question 8

What is the token passing model of a UML activity diagram?

Answer 8

• tokens created at initial node
• puhsed through graph
• routed at descisions, collected at merges
• replicated at forks, merged at joins
• consumed at final nodes