Informatics 121 Software Design I Lecture 3 Duplication
- Slides: 45
Informatics 121 Software Design I Lecture 3 Duplication of course material for any commercial purpose without the explicit written permission of the professor is prohibited. SDCL Software Design and Collaboration Laboratory Department of Informatics, UC Irvine sdcl. ics. uci. edu 1
Today • Design cycle SDCL Software Design and Collaboration Laboratory Department of Informatics, UC Irvine sdcl. ics. uci. edu 2
Design • To decide upon a plan for change in the world that, when realized, satisfies stakeholders SDCL Software Design and Collaboration Laboratory Department of Informatics, UC Irvine sdcl. ics. uci. edu 3
Design problem and solution design problem SDCL Software Design and Collaboration Laboratory design solution Department of Informatics, UC Irvine sdcl. ics. uci. edu 4
Design project design problem design solution design project SDCL Software Design and Collaboration Laboratory Department of Informatics, UC Irvine sdcl. ics. uci. edu 5
Design cycle synthesize analyze SDCL Software Design and Collaboration Laboratory evaluate Department of Informatics, UC Irvine sdcl. ics. uci. edu 6
Design cycle synthesize analyze SDCL Software Design and Collaboration Laboratory goals constraints assumptions decisions ideas Department of Informatics, UC Irvine evaluate sdcl. ics. uci. edu 7
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 SDCL Software Design and Collaboration Laboratory Department of Informatics, UC Irvine sdcl. ics. uci. edu 8
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 SDCL Software Design and Collaboration Laboratory Department of Informatics, UC Irvine sdcl. ics. uci. edu 9
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 SDCL Software Design and Collaboration Laboratory Department of Informatics, UC Irvine sdcl. ics. uci. edu 10
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 SDCL Software Design and Collaboration Laboratory Department of Informatics, UC Irvine sdcl. ics. uci. edu 11
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 SDCL Software Design and Collaboration Laboratory Department of Informatics, UC Irvine sdcl. ics. uci. edu 12
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 SDCL Software Design and Collaboration Laboratory Department of Informatics, UC Irvine sdcl. ics. uci. edu 13
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 SDCL Software Design and Collaboration Laboratory Department of Informatics, UC Irvine sdcl. ics. uci. edu 14
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 SDCL Software Design and Collaboration Laboratory Department of Informatics, UC Irvine sdcl. ics. uci. edu 15
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 SDCL Software Design and Collaboration Laboratory Department of Informatics, UC Irvine sdcl. ics. uci. edu 16
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 SDCL Software Design and Collaboration Laboratory Department of Informatics, UC Irvine sdcl. ics. uci. edu 17
Design cycle at the micro level: design work synthesize analyze SDCL Software Design and Collaboration Laboratory goals constraints assumptions decisions ideas Department of Informatics, UC Irvine evaluate sdcl. ics. uci. edu 18
Design work • Design work represents the individual or collaborative activity of engaging with a design project at a detailed level – – – – SDCL thinking articulating context analyzing alternative ideas identifying constraints making decisions setting goals … Software Design and Collaboration Laboratory Department of Informatics, UC Irvine sdcl. ics. uci. edu 19
Opportunistic versus rationalistic design work unexplored idea SDCL Software Design and Collaboration Laboratory current decision Department of Informatics, UC Irvine sdcl. ics. uci. edu 20
Mixed opportunistic and rationalistic design work unexplored idea SDCL Software Design and Collaboration Laboratory current decision Department of Informatics, UC Irvine sdcl. ics. uci. edu 21
Backtracking unexplored idea previous decision explored idea current decision SDCL Software Design and Collaboration Laboratory Department of Informatics, UC Irvine sdcl. ics. uci. edu 22
Backtracking unexplored idea previous decision explored idea current decision SDCL Software Design and Collaboration Laboratory Department of Informatics, UC Irvine sdcl. ics. uci. edu 23
Simultaneous exploration unexplored idea SDCL Software Design and Collaboration Laboratory current decision Department of Informatics, UC Irvine sdcl. ics. uci. edu 24
Design cycle at the macro level: design process synthesize analyze SDCL Software Design and Collaboration Laboratory goals constraints assumptions decisions ideas Department of Informatics, UC Irvine evaluate sdcl. ics. uci. edu 25
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 SDCL Software Design and Collaboration Laboratory Department of Informatics, UC Irvine sdcl. ics. uci. edu 26
Linear process what is it to accomplish? satisfactory experience how does one interact with it? change in the world what is its conceptual core? plan for realization what are its implementation details? SDCL Software Design and Collaboration Laboratory Department of Informatics, UC Irvine sdcl. ics. uci. edu 27
Waterfall requirements phase design phase implementation phase testing phase SDCL Software Design and Collaboration Laboratory Department of Informatics, UC Irvine sdcl. ics. uci. edu 28
Waterfall as a design process what is it to accomplish? satisfactory experience how does one interact with it? change in the world what is its conceptual core? plan for realization what are its implementation details? SDCL Software Design and Collaboration Laboratory Department of Informatics, UC Irvine sdcl. ics. uci. edu 29
Agile • • • SDCL 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. Software Design and Collaboration Laboratory • • • 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. ics. uci. edu 30
Agile as a design process what is it to accomplish? satisfactory experience how does one interact with it? change in the world what is its conceptual core? plan for realization what are its implementation details? SDCL Software Design and Collaboration Laboratory Department of Informatics, UC Irvine sdcl. ics. uci. edu 31
Other life cycle models • Extreme programming • Rapid prototyping • Spiral model • Iterative development • Rational unified process • Synchronize-and-stabilize • … SDCL Software Design and Collaboration Laboratory Department of Informatics, UC Irvine sdcl. ics. uci. edu 32
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 SDCL Software Design and Collaboration Laboratory Department of Informatics, UC Irvine sdcl. ics. uci. edu 33
Design is a wicked problem • The problem is not understood until after the formulation of a solution • Wicked problems have no stopping rule • Solutions to wicked problems are not right or wrong • Every wicked problem is essentially novel and unique • Every solution to a wicked problem is a “one shot operation” • Wicked problems have no given alternative solutions To decide upon a plan for change in the world that, when realized, satisfies stakeholders SDCL Software Design and Collaboration Laboratory Department of Informatics, UC Irvine sdcl. ics. uci. edu 34
From software life cycles to design methods design problem design solution design project Which set of design methods is appropriate to use, when, to successfully complete a design project? SDCL Software Design and Collaboration Laboratory Department of Informatics, UC Irvine sdcl. ics. uci. edu 35
Choosing design methods to apply • Focus on essence • Focus on the unknown • Focus on making progress SDCL Software Design and Collaboration Laboratory Department of Informatics, UC Irvine sdcl. ics. uci. edu 36
Focus on essence • Every design problem has an essence, the key – and often most difficult – part that must be understood and addressed ‘right’ for the design solution (plan for change in the world) to satisfy the stakeholders • Postponing understanding and addressing the essence of a design problem incurs a significant risk of rework at a later time SDCL Software Design and Collaboration Laboratory Department of Informatics, UC Irvine sdcl. ics. uci. edu 37
Focus on the unknown • Every design problem involves knowledge deficiencies – gaps in the understanding of the design problem and its possible solutions – that must be addressed for the design solution (plan for change in the world) to satisfy the stakeholders • Postponing understanding and addressing knowledge deficiencies incurs a significant risk of rework at a later time SDCL Software Design and Collaboration Laboratory Department of Informatics, UC Irvine sdcl. ics. uci. edu 38
Focus on making progress • Every design problem involves times during which the design project gets stuck; focusing effort elsewhere and continuing to make progress is often the right approach in response • Continuing to focus on a stuck issue for extended periods of time tends to be effort that is wasted SDCL Software Design and Collaboration Laboratory Department of Informatics, UC Irvine sdcl. ics. uci. edu 39
Realistic design process what is it to accomplish? satisfactory experience how does one interact with it? change in the world what is its conceptual core? plan for realization what are its implementation details? SDCL Software Design and Collaboration Laboratory Department of Informatics, UC Irvine sdcl. ics. uci. edu 40
Backtracking is inevitable here, too what is it to accomplish? satisfactory experience how does one interact with it? change in the world what is its conceptual core? plan for realization what are its implementation details? SDCL Software Design and Collaboration Laboratory Department of Informatics, UC Irvine sdcl. ics. uci. edu 41
Minimize backtracking what is it to accomplish? satisfactory experience how does one interact with it? change in the world what is its conceptual core? plan for realization what are its implementation details? • Strive to minimize backtracking more than absolutely necessary • Strive to minimize backtracking later than absolutely necessary SDCL Software Design and Collaboration Laboratory Department of Informatics, UC Irvine sdcl. ics. uci. edu 42
high Routine, adaptive, and original design projects complexity original adaptive low routine high low familiarity SDCL Software Design and Collaboration Laboratory Department of Informatics, UC Irvine sdcl. ics. uci. edu 43
Design studio 1 • You are tasked with designing “social table”, a software system that enables restaurant customers to place orders, but also socially interact about their others with others in the restaurant (and perhaps beyond) • Identify – audience – other stakeholders • Identify – goals – constraints • Clearly document these in a typewritten document, to be handed in on Thursday, October 17, at the beginning of class SDCL Software Design and Collaboration Laboratory Department of Informatics, UC Irvine sdcl. ics. uci. edu 44
Design studio 1 • Assignment is on an individual basis, but will be continued in class on Thursday • You should focus on generating broad lists; that is, as many items in each list as possible – four separate lists (audience, stakeholders, goals, constraints) • The overall focus is on brainstorming – your document does not need to have lengthy narratives (but should be clear) SDCL Software Design and Collaboration Laboratory Department of Informatics, UC Irvine sdcl. ics. uci. edu 45
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