© 2010 university of california, irvine – andré van der hoek1june 14, 2015 – 15:24:35...
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© 2010 University of California, Irvine – André van der Hoek 1April 18, 2023 – 20:56:21
Informatics 121Software Design IInformatics 121
Software Design I
Lecture 11
André van der Hoek & Alex Baker
Duplication of course material for any commercial purpose without the explicit written permission of the professor is prohibited.
Today’s LectureToday’s Lecture
Design rationale
In-class design exercise
© 2010 University of California, Irvine – André van der Hoek 2April 18, 2023 – 20:56:21
A Simple QuestionA Simple Question
Why is a given design as it is?
© 2010 University of California, Irvine – André van der Hoek 3April 18, 2023 – 20:56:21
A Difficult AnswerA Difficult Answer
Any design involves 100s if not 1000s of decisions that are tough to all remember
Worse yet, any design involves 100s if not 1000s of discussions, considerations of alternatives, and reasons why certain choices are made, which are even tougher to all remember
© 2010 University of California, Irvine – André van der Hoek 4April 18, 2023 – 20:56:21
A Difficult AnswerA Difficult Answer
Any design involves 100s if not 1000s of decisions that are tough to all remember
Worse yet, any design involves 100s if not 1000s of discussions, considerations of alternatives, and reasons why certain choices are made, which are even tougher to all remember
Especially three months later, a year later, two years later…
© 2010 University of California, Irvine – André van der Hoek 5April 18, 2023 – 20:56:21
Knowing Why Is A Crucial NeedKnowing Why Is A Crucial Need
Helps explain particular features to the customer
Helps assist with coding
Helps build a shared understanding of the design among a team of designers
Helps guide maintenance and other design changes– evolution– roadblocks
Helps reflect on one’s own design practices
© 2010 University of California, Irvine – André van der Hoek 6April 18, 2023 – 20:56:21
SketchbooksSketchbooks
© 2010 University of California, Irvine – André van der Hoek 7April 18, 2023 – 20:56:21
SketchbooksSketchbooks
© 2010 University of California, Irvine – André van der Hoek 8April 18, 2023 – 20:56:21
SketchbooksSketchbooks
© 2010 University of California, Irvine – André van der Hoek 9April 18, 2023 – 20:56:21
Software “Sketchbooks”Software “Sketchbooks”
If they exist, they tend to be text, text, text, text, text, and the occasional picture of a whiteboard…
Maybe an architecture diagram
Maybe a UML diagram
…
© 2010 University of California, Irvine – André van der Hoek 10April 18, 2023 – 20:56:21
Design DecisionsDesign Decisions
Explicitly recognizing design decisions helps in documenting the “design space”, and at least articulating the available choices
Some of your homeworks even discuss tradeoffs, and motivate the choices you make for your final design– though typically ignoring any intermediate decisions that
may have been made to which you later may need to return
The actual rationale, though, tends to be quite small in comparison to design decisions– and reconstructing it is difficult
© 2010 University of California, Irvine – André van der Hoek 11April 18, 2023 – 20:56:21
An ExampleAn Example
© 2010 University of California, Irvine – André van der Hoek 12April 18, 2023 – 20:56:21
Design RationaleDesign Rationale
Design rationale is focused on capturing a historical record of the analysis that led to the choice of a particular artifact or feature in question, and in the most general sense is an explanation of why something is designed the way it is
Design rationale involves explicit capture of the design decisions that shaped a particular software system and the reasons for those decisions (‘know-why’ knowledge)
© 2010 University of California, Irvine – André van der Hoek 13April 18, 2023 – 20:56:21
Design RationaleDesign Rationale
Descriptive– retroactive– aims to communicate a design’s intent
Prescriptive– in-the-moment– aims to improve the design process
© 2010 University of California, Irvine – André van der Hoek 14April 18, 2023 – 20:56:21
Modern VariantModern Variant
© 2010 University of California, Irvine – André van der Hoek 17April 18, 2023 – 20:56:21
Design HistoriesDesign Histories
Expand on design rationale by capturing design processes as they occur over time, as most design does not take place in a single meeting
More focused on description than prescription to date
© 2010 University of California, Irvine – André van der Hoek 18April 18, 2023 – 20:56:21
Alex’ HomegrownAlex’ Homegrown
© 2010 University of California, Irvine – André van der Hoek 20April 18, 2023 – 20:56:21
In-Class Design ExerciseIn-Class Design Exercise
Collectively, using the tablets and Calico, design a history representation that you could have used for the previous assignment (or use for the next assignment)
Use your tablets to support your verbal contributions, annotate our design in progress, develop another idea in parallel, etc.
Remember stakeholders, goals, audience, uses, …
Remember techniques and notations available
© 2010 University of California, Irvine – André van der Hoek 21April 18, 2023 – 20:56:21