Department of Informatics, UC Irvine SDCL Collaboration Laboratory Software Design and sdcl.ics.uci.edu 1 Informatics 121 Software Design I Lecture 2 Duplication of course material for any commercial purpose without the explicit written permission of the professor is prohibited.

Department of Informatics, UC Irvine SDCL Collaboration Laboratory Software Design and sdcl.ics.uci.edu 2 Discussion There will be discussion this Friday Please join your designated discussion Note new classroom: SE2 1304

Department of Informatics, UC Irvine SDCL Collaboration Laboratory Software Design and sdcl.ics.uci.edu 3 Intermezzo: what experts do Experts prefer simple solutions Experts solve simpler problems first Experts divide and conquer Experts do not overgeneralize Experts design elegant abstractions Experts use metaphor

Department of Informatics, UC Irvine SDCL Collaboration Laboratory Software Design and sdcl.ics.uci.edu 4 Today Defining design Feasibility and desirability Four types of design Design cycle

Department of Informatics, UC Irvine SDCL Collaboration Laboratory Software Design and sdcl.ics.uci.edu 5 Three themes 1.Design focuses on identifying a novel envisioned future 2.Design involves deliberate decision making and planning; it is not simply acting out of impulse 3.Design decisions are consequential: there are stakeholders who must be satisfied with the result

Department of Informatics, UC Irvine SDCL Collaboration Laboratory Software Design and sdcl.ics.uci.edu 6 Our definition To decide upon a plan for a novel change in the world that, when realized, satisfies stakeholders

Department of Informatics, UC Irvine SDCL Collaboration Laboratory Software Design and sdcl.ics.uci.edu 7 Design designerplan makerchange in the world audienceexperiences other stakeholders

Department of Informatics, UC Irvine SDCL Collaboration Laboratory Software Design and sdcl.ics.uci.edu 8 Design a luxury airplane designerplan makerchange in the world audienceexperiences other stakeholders

Department of Informatics, UC Irvine SDCL Collaboration Laboratory Software Design and sdcl.ics.uci.edu 9 Design a library designerplan makerchange in the world audienceexperiences other stakeholders

Department of Informatics, UC Irvine SDCL Collaboration Laboratory Software Design and sdcl.ics.uci.edu 10 Design an award designerplan makerchange in the world audienceexperiences other stakeholders

Department of Informatics, UC Irvine SDCL Collaboration Laboratory Software Design and sdcl.ics.uci.edu 11 Design fields Architecture design Graphic design Fashion design Game design Chip design Car design Urban design Product design Interior design …

Department of Informatics, UC Irvine SDCL Collaboration Laboratory Software Design and sdcl.ics.uci.edu 12 Design fields Architecture design Graphic design Fashion design Game design Chip design Car design Urban design Product design Interior design … Writing Painting Sculpting Music composition …

Department of Informatics, UC Irvine SDCL Collaboration Laboratory Software Design and sdcl.ics.uci.edu 13 Design fields Architecture design Graphic design Fashion design Game design Chip design Car design Urban design Product design Interior design … Writing Painting Sculpting Music composition … Software design

Department of Informatics, UC Irvine SDCL Collaboration Laboratory Software Design and sdcl.ics.uci.edu 14 Design designerplan makerchange in the world audienceexperiences other stakeholders

Department of Informatics, UC Irvine SDCL Collaboration Laboratory Software Design and sdcl.ics.uci.edu 15 Software design software designersource code compiler * runnable program usersexperiences other stakeholders [ * or, at times, the person who installs and configures the software instead of the compiler]

Department of Informatics, UC Irvine SDCL Collaboration Laboratory Software Design and sdcl.ics.uci.edu 16 Feasibility and desirability designerplan maker audienceexperiences other stakeholders feasibility change in the world

Department of Informatics, UC Irvine SDCL Collaboration Laboratory Software Design and sdcl.ics.uci.edu 17 Feasibility and desirability designerplan makerchange in the world audience other stakeholders desirability experiences feasibility

Department of Informatics, UC Irvine SDCL Collaboration Laboratory Software Design and sdcl.ics.uci.edu 18 Four types of design desirability feasibility what is it to accomplish? how does one interact with it? what is its conceptual core? what are its implementation details?

Department of Informatics, UC Irvine SDCL Collaboration Laboratory Software Design and sdcl.ics.uci.edu 19 Four types of design satisfactory experience plan for realization change in the world what is it to accomplish? how does one interact with it? what is its conceptual core? what are its implementation details?

Department of Informatics, UC Irvine SDCL Collaboration Laboratory Software Design and sdcl.ics.uci.edu 20 Four types of software design satisfactory experience plan for realization change in the world what is it to accomplish? how does one interact with it? what is its conceptual core? what are its implementation details? application design interaction design architecture design implementation design

Department of Informatics, UC Irvine SDCL Collaboration Laboratory Software Design and sdcl.ics.uci.edu 21 Design an instant message system satisfactory experience plan for realization change in the world what is it to accomplish? how does one interact with it? what is its conceptual core? what are its implementation details? application design interaction design architecture design implementation design

Department of Informatics, UC Irvine SDCL Collaboration Laboratory Software Design and sdcl.ics.uci.edu 22 Design a word processor satisfactory experience plan for realization change in the world what is it to accomplish? how does one interact with it? what is its conceptual core? what are its implementation details? application design interaction design architecture design implementation design

Department of Informatics, UC Irvine SDCL Collaboration Laboratory Software Design and sdcl.ics.uci.edu 23 Design problem and solution design problemdesign solution

Department of Informatics, UC Irvine SDCL Collaboration Laboratory Software Design and sdcl.ics.uci.edu 24 Design project design problemdesign solution design project

Department of Informatics, UC Irvine SDCL Collaboration Laboratory Software Design and sdcl.ics.uci.edu 25 Design cycle analyzeevaluate synthesize

Department of Informatics, UC Irvine SDCL Collaboration Laboratory Software Design and sdcl.ics.uci.edu 26 Design cycle analyzeevaluate synthesize goals constraints assumptions decisions ideas

Department of Informatics, UC Irvine SDCL Collaboration Laboratory Software Design and sdcl.ics.uci.edu 27 Goals A goal represents an explicit acknowledgment of a desired result that the eventual design solution must achieve Goals may be suggested by any of the stakeholders – client – other stakeholders – audience – designer Goals change over time, and may or may not be (partially) addressed by the current state of the design solution

Department of Informatics, UC Irvine SDCL Collaboration Laboratory Software Design and sdcl.ics.uci.edu 28 Example goals The luxury airplane must be 10% more fuel-efficient than its predecessor The library must be able to hold 250,000 books The award must be representative of the professional society that is commissioning it

Department of Informatics, UC Irvine SDCL Collaboration Laboratory Software Design and sdcl.ics.uci.edu 29 Constraints A constraint represents an explicit acknowledgment of a condition that restricts the design project Constraints may be suggested by any of the stakeholders – client – other stakeholders – audience – designer Constraints change over time, and may or may not be (partially) met by the current state of the design project

Department of Informatics, UC Irvine SDCL Collaboration Laboratory Software Design and sdcl.ics.uci.edu 30 Example constraints The luxury airplane must weigh less than 50,000 pounds The library must not violate federal disability laws The award must cost less than $1000 to produce

Department of Informatics, UC Irvine SDCL Collaboration Laboratory Software Design and sdcl.ics.uci.edu 31 Assumptions An assumption represents a fact that is taken for granted, may or may not be true, and influences the design project Assumptions may be made by any of the stakeholders – client – other stakeholders – audience – designer Assumptions change over time, and may or may not be (partially) fulfilled by the current state of the design project

Department of Informatics, UC Irvine SDCL Collaboration Laboratory Software Design and sdcl.ics.uci.edu 32 Example assumptions The average person weighs 85 kilograms The library needs to serve the community with an area stocked with personal computers The professional society’s logo is red and white, which therefore must be its preferred colors for the award

Department of Informatics, UC Irvine SDCL Collaboration Laboratory Software Design and sdcl.ics.uci.edu 33 Decisions A decision represents a specific choice of how to further the design solution, typically after some amount of consideration Decisions are the sole responsibility of the designer, though they can be (heavily) influenced by other stakeholders Decisions change over time, and new decisions may or may not (partially) align with the current state of the design project

Department of Informatics, UC Irvine SDCL Collaboration Laboratory Software Design and sdcl.ics.uci.edu 34 Example decisions The fuselage and wings of the luxury airplane shall be made out of carbon composites The library shall have bookshelves that are not movable The award shall be made out of colored glass

Department of Informatics, UC Irvine SDCL Collaboration Laboratory Software Design and sdcl.ics.uci.edu 35 Idea An idea represents a thought or opinion, ranging from highly unformed to fully formed, that potentially shapes the design solution Ideas typically are the sole responsibility of the designer, though they may be inspired by many different sources Ideas change over time, and new ideas may or may not (partially) align with the current state of the design project

Department of Informatics, UC Irvine SDCL Collaboration Laboratory Software Design and sdcl.ics.uci.edu 36 Example ideas What if the luxury airplane had a shower on board? Perhaps the library membership cards should have RFID tags, so a visitor can simply grab the books they want, walk by an automated scanner, and have their books be on loan I am thinking that the award should be a variant of last year’s award

Department of Informatics, UC Irvine SDCL Collaboration Laboratory Software Design and sdcl.ics.uci.edu 37 Design an instant message system analyzeevaluate synthesize goals constraints assumptions decisions ideas

Department of Informatics, UC Irvine SDCL Collaboration Laboratory Software Design and sdcl.ics.uci.edu 38 Design a word processor analyzeevaluate synthesize goals constraints assumptions decisions ideas

Department of Informatics, UC Irvine SDCL Collaboration Laboratory Software Design and sdcl.ics.uci.edu 39 Design the software to fly a drone analyzeevaluate synthesize goals constraints assumptions decisions ideas

Department of Informatics, UC Irvine SDCL Collaboration Laboratory Software Design and sdcl.ics.uci.edu 40 Design cycle at the micro level: design work analyzeevaluate synthesize goals constraints assumptions decisions ideas

Department of Informatics, UC Irvine SDCL Collaboration Laboratory Software Design and sdcl.ics.uci.edu 41 Design work Design work represents the individual or collaborative activity of engaging with a design project at a detailed level – thinking – articulating context – analyzing alternative ideas – identifying constraints – making decisions – setting goals – …

Department of Informatics, UC Irvine SDCL Collaboration Laboratory Software Design and sdcl.ics.uci.edu 42 current decisionexplored idea Opportunistic versus rationalistic design work unexplored idea

Department of Informatics, UC Irvine SDCL Collaboration Laboratory Software Design and sdcl.ics.uci.edu 43 Mixed opportunistic and rationalistic design work current decisionexplored idea unexplored idea

Department of Informatics, UC Irvine SDCL Collaboration Laboratory Software Design and sdcl.ics.uci.edu 44 Backtracking current decisionexplored idea unexplored ideaprevious decision

Department of Informatics, UC Irvine SDCL Collaboration Laboratory Software Design and sdcl.ics.uci.edu 45 Backtracking current decisionexplored idea unexplored ideaprevious decision

Department of Informatics, UC Irvine SDCL Collaboration Laboratory Software Design and sdcl.ics.uci.edu 46 Simultaneous exploration current decisionexplored idea unexplored idea

Department of Informatics, UC Irvine SDCL Collaboration Laboratory Software Design and sdcl.ics.uci.edu 47 Design an instant message system analyzeevaluate synthesize goals constraints assumptions decisions ideas

Department of Informatics, UC Irvine SDCL Collaboration Laboratory Software Design and sdcl.ics.uci.edu 48 Design a word processor analyzeevaluate synthesize goals constraints assumptions decisions ideas

Department of Informatics, UC Irvine SDCL Collaboration Laboratory Software Design and sdcl.ics.uci.edu 49 Design the software to fly a drone analyzeevaluate synthesize goals constraints assumptions decisions ideas

Department of Informatics, UC Irvine SDCL Collaboration Laboratory Software Design and sdcl.ics.uci.edu 50 Design cycle at the macro level: design process analyzeevaluate synthesize goals constraints assumptions decisions ideas

Department of Informatics, UC Irvine SDCL Collaboration Laboratory Software Design and sdcl.ics.uci.edu 51 Design process A design process represents a planned course of action as to how to tackle a design problem to arrive at a design solution – where to focus effort – what methods to use – whom to involve A design process may be defined up-front in its entirety, or defined in increments as the design project unfolds

Department of Informatics, UC Irvine SDCL Collaboration Laboratory Software Design and sdcl.ics.uci.edu 52 Linear process satisfactory experience plan for realization change in the world what is it to accomplish? how does one interact with it? what is its conceptual core? what are its implementation details?

Department of Informatics, UC Irvine SDCL Collaboration Laboratory Software Design and sdcl.ics.uci.edu 53 Waterfall requirements phase design phase implementation phase testing phase

Department of Informatics, UC Irvine SDCL Collaboration Laboratory Software Design and sdcl.ics.uci.edu 54 Waterfall as a design process satisfactory experience plan for realization change in the world what is it to accomplish? how does one interact with it? what is its conceptual core? what are its implementation details?

Department of Informatics, UC Irvine SDCL Collaboration Laboratory Software Design and sdcl.ics.uci.edu 55 Agile Our highest priority is to satisfy the customer through early and continuous delivery of valuable software. Welcome changing requirements, even late in development. Agile processes harness change for the customer's competitive advantage. Deliver working software frequently, from a couple of weeks to a couple of months, with a preference to the shorter timescale. Business people and developers must work together daily throughout the project. Build projects around motivated individuals. Give them the environment and support they need, and trust them to get the job done. The most efficient and effective method of conveying information to and within a development team is face-to-face conversation. Working software is the primary measure of progress. Agile processes promote sustainable development. The sponsors, developers, and users should be able to maintain a constant pace indefinitely. Continuous attention to technical excellence and good design enhances agility. Simplicity—the art of maximizing the amount of work not done—is essential. The best architectures, requirements, and designs emerge from self-organizing teams. At regular intervals, the team reflects on how to become more effective, then tunes and adjusts its behavior accordingly.

Department of Informatics, UC Irvine SDCL Collaboration Laboratory Software Design and sdcl.ics.uci.edu 56 Agile as a design process satisfactory experience plan for realization change in the world what is it to accomplish? how does one interact with it? what is its conceptual core? what are its implementation details?

Department of Informatics, UC Irvine SDCL Collaboration Laboratory Software Design and sdcl.ics.uci.edu 57 Other life cycle models Extreme programming Rapid prototyping Spiral model Iterative development Rational unified process Synchronize-and-stabilize …

Department of Informatics, UC Irvine SDCL Collaboration Laboratory Software Design and sdcl.ics.uci.edu 58 Choosing a software life cycle Choosing a software life cycle is choosing a design process One has to make sure the design process matches the nature of the design problem One has to make sure to remain flexible in adjusting the design process when the project so warrants

Department of Informatics, UC Irvine SDCL Collaboration Laboratory Software Design and sdcl.ics.uci.edu 59 Routine, adaptive, and original design projects high low complexity highlow familiarity routine adaptive original

Department of Informatics, UC Irvine SDCL Collaboration Laboratory Software Design and sdcl.ics.uci.edu 60 Design an instant message system high low complexity highlow familiarity routine adaptive original

Department of Informatics, UC Irvine SDCL Collaboration Laboratory Software Design and sdcl.ics.uci.edu 61 Design a word processor high low complexity highlow familiarity routine adaptive original

Department of Informatics, UC Irvine SDCL Collaboration Laboratory Software Design and sdcl.ics.uci.edu 62 Design the software to fly a drone high low complexity highlow familiarity routine adaptive original

Department of Informatics, UC Irvine SDCL Collaboration Laboratory Software Design and sdcl.ics.uci.edu 63 Realistic design process satisfactory experience plan for realization change in the world what is it to accomplish? how does one interact with it? what is its conceptual core? what are its implementation details?

Department of Informatics, UC Irvine SDCL Collaboration Laboratory Software Design and sdcl.ics.uci.edu 64 Backtracking is inevitable here, too satisfactory experience plan for realization change in the world what is it to accomplish? how does one interact with it? what is its conceptual core? what are its implementation details?

Department of Informatics, UC Irvine SDCL Collaboration Laboratory Software Design and sdcl.ics.uci.edu 65 Minimize backtracking satisfactory experience plan for realization change in the world what is it to accomplish? how does one interact with it? what is its conceptual core? what are its implementation details? Strive to minimize backtracking more than absolutely necessary Strive to minimize backtracking later than absolutely necessary