Lecture 4: Capturing Design Rationale

Question 1

What is the difference between a decisioin problem and a design problem?

Answer 1

•  Decision problems are defined by a fixed set of options to choose among
•  Design problems are more than complex, they are dilemmas

Question 2

What are the 3 types of information of service contracts?

Answer 2

• functional requirements
• non functional requirements
• design decisions

Question 3

What is the states of the design?

Answer 3

• decisions taken
• decisions left pending
• concerns/ issues that need to be refined and articulated as decisions
• concerns/issues that are left out

Question 4

Classification of the design decisions?

Legenda:
DT = decision, Taken
DP = decision, left Pending
IR = issue, needing Refinement (articulated as decision)
IO = issue, left Out

Answer 4

• DT: grant system acces to end-users depending on their role
• DP: Duplicate/distribute data on multiple DB servers
• DP: secre data exchange against unauthorized data acces
• IR: ensure data availablity
• IO: ensure good level of usability

Question 5

How to move forward in the design process?

Answer 5

Make assumptions:

• Assumptions are ‘hypotheses about the problem and the context of its solution’
• they may later prove to be unfounded
• many are typically left implicit.

Question 6

Design rationale:

Answer 6

1. The logical reasons given to justify a designed artifact, for someone.
2. An explanation of why a designed artifact is the way it is, for some concern/issue

Question 7

Formal capture techniques

Answer 7

predicates logic, constrain expression to a predefined set of categories
+ codified
- inhibit or constrain deliberation

Question 8

Informal capture techniques

Answer 8

+ capture wide range of considerations

Active: mind-mapping
- require considerable discipline
Passive: video recording
- postpone the effort of searching and organizing

Question 9

What is a QOC

Answer 9

Questions: key design issues
Options: possible answers
Criteria: assess and compare the options