Informatics 122 Software Design II Lecture 12 Emily Navarro Duplication of course material for any commercial purpose without the explicit written permission of the professor is prohibited. 1

Today’s Lecture Course wrap-up

What did we learn? Design aesthetics Design patterns Refactoring Design recovery Reuse Design in the large Design techniques

Purpose of Implementation Design An implementation design is a road map understandable, unambiguous, consistent, helpful, … An implementation design describes a path from application / interaction / architecture design to the product correct, complete, concise, verifiable, effective, … An implementation design describes what the implementers should do elegant, partitionable, recomposable, resilient, … An implementation design is a guide towards future change evolvable, …

More of a Shared Understanding (Not Perfect!) An implementation design is a road map understandable, unambiguous, consistent, helpful, … An implementation design describes a path from application / interaction / architecture design to the product correct, complete, concise, verifiable, effective, … An implementation design describes what the implementers should do elegant, partitionable, recomposable, resilient, … An implementation design is a guide towards future change evolvable, …

Less of a Shared Understanding An implementation design is a road map understandable, unambiguous, consistent, helpful, … An implementation design describes a path from application / interaction / architecture design to the product correct, complete, concise, verifiable, effective, … An implementation design describes what the implementers should do elegant, partitionable, recomposable, resilient, … An implementation design is a guide towards future change evolvable, …

Designing for Change Change abounds! Designing for change is a matter of: Controlling dependency Proper encapsulation Generalizing where you can Which changes? What are the biggest change risks? What kind of program is this, essentially? Where is “the line”? What do we know we will have? Put this in an interface What variations on that might we see? Hide this behind the interface

Design Patterns Design patterns let us reuse solutions that have worked in the past Design patterns show us how to apply good design practices Patterns covered Strategy Adapter Factory Method Abstract Factory Template Method Singleton Facade

Refactoring Refactoring is a useful technique for making non- functional changes to a software system that result in better code structures less code more easily understandable code Bad Smells Useful analogy for discovering places in a system “ripe” for refactoring Remember to test constantly!

Design Recovery Recreating design abstractions from: Code Existing design documentation (if available) Personal experience / general knowledge about problem and application domains Talking to people You will work with code in the absence of a complete design (Biggerstaff, 1989)

Component Reuse Component reuse is using an already-developed piece of software (usually from a third-party) to provide some type of functionality to your system rather than developing the functionality yourself from scratch identify preliminary architecture identify potential places for reuse establish selection criteria (per place) search for applicable components evaluate components select component update architecture

Design-in-the-Large Main challenge: Maintaining a unified design vision Multiple views will be necessary (unless you’re “agile”)

Other Design Techniques Commonality and Variability Analysis (CVA) Used to identify the commonalities (generic concepts) and variations (concrete implementations) in a problem domain Analysis Matrix Used to help designers deal with large amounts of variation in a problem domain Such techniques allow you to use the principles from design patterns in any design

Practice, Practice, Practice… To learn to navigate this space, and learn to be a designer, it is essential to practice, practice, practice There is no theory or magic formula that will teach you to be a designer, only theory that will help you understand what it means to be a designer provides you with a frame of mind through which you can usefully reflect upon your design activities and design products

Thank you!