+ Informatics 122 Software Design II Lecture 6 Emily Navarro Duplication of course material for any commercial purpose without the explicit written permission of the professor is prohibited. 1

+ Today’s Lecture Design aesthetics Your BeNumbered designs 2

+ But first… A Few Updates about Assignment 2 Deadline extended to Tuesday, February 4 Remember, no real GUI is required But you should show the intermediate boards after each sequence is removed but before the spaces are filled in with random numbers and after the spaces are filled in with random numbers 3

+ Design Aesthetics What makes a given software implementation design “beautiful”? What is it that makes someone appreciate a particular software implementation design? What are the qualities that determine whether a particular software implementation design is “good” or “bad”? What is it, then, that we can strive for in creating a software implementation design that will help others in appreciating it? 4

+ Purpose of Implementation Design An implementation design is a road map An implementation design describes a path from application / interaction / architecture design to the product An implementation design describes what the implementers should do An implementation design is a guide towards future change 5

+ Purpose of Implementation Design An implementation design is a road map understandable, unambiguous, consistent, helpful, … uses a good naming schema An implementation design describes a path from application / interaction / architecture design to the product correct, complete, concise, verifiable, effective, … attention to detail, well-documented, has clear flow, has a clear layout, has a clear interaction between classes, uses UML syntax correctly An implementation design describes what the implementers should do elegant, partitionable, recomposable, resilient, … An implementation design is a guide towards future change evolvable, … 6

+ Less of a Shared Understanding An implementation design is a road map understandable, unambiguous, consistent, helpful, … uses a good naming schema An implementation design describes a path from application / interaction / architecture design to the product correct, complete, concise, verifiable, effective, … attention to detail, well-documented, has clear flow, has a clear layout, has a clear interaction between classes, uses UML syntax correctly An implementation design describes what the implementers should do elegant, partitionable, recomposable, resilient, … An implementation design is a guide towards future change evolvable, … 7

+ Some Caveats We are going to be showing, praising, and critiquing your designs not to ridicule, rather to provide constructive feedback This is a normal part of any design studio class Rules of the game do not identify someone, even if you know whose design it is someone may choose to volunteer and explain their design, but they may also choose not to do so We only highlight parts of certain designs, so please do not correlate our comments here with your final grade for this assignment 8

+ Designs Rated Highly By Peers

+ Some “Obvious” Room for Improvement

+ Important Points to Observe (Assignment) Being a “1” or a “5” on someone’s ranking is not an absolute evaluation if you are a “1” on someone’s ranking, the other designs may have all been relatively poor if you are a “5” on someone’s ranking, the other designs may have all been relatively stellar Length of the document may be an indicator in peer’s rankings, but not necessarily in ours It is easier to review than to design, or is it? 11

+ Important Points to Observe (UML) Having a document “heavy on UML” by itself is not a guarantee for a great design it may indeed be more complete it may also be less understandable If we cannot find the “flow” in the UML diagram, something tends to be wrong for some designs, we end up searching for their meaning for others, it is clear from the diagram physical layout, often, has something to do with this Design languages are a factor UML by itself is insufficient 12

+ Important Points to Observe (Process) Where to start? what about with the set of nouns in the description of the problem (e.g., grid, cell, sequence, flame number, …) what about with the set of verbs in the description of the problem (e.g., chooses adjacent cells, cells are swapped, cells are emptied …) Work towards completeness does my current design account for all possible features does it do so explicitly, or are some features hidden This is merely a rough and rules of thumb process, but one that tends to help the beginning designer 13

+ A Checklist for the Overall Process Apply rigor Separate concerns modularize abstract Anticipate change Generalize Work incrementally 14

+ A Checklist for Overall Design Strive for grouping related functionality (high cohesion) Strive for ungrouping semi-related functionality (high cohesion) Strive for reducing interdependency (low coupling) 15

+ A Checklist on Class Design Cohesion Completeness Convenience Clarity Consistency 16

+ A Checklist on Principles and Strategies Principles keep it simple, stupid! (KISS) information hiding acyclic dependencies … Strategies program to the interface refactor apply software patterns … 17