Informatics 121 Software Design I

Informatics 121Software Design I Lecture 3 Duplication of course material for any commercial purpose without the explicit written permission of the professor is prohibited.

Today • Design cycle

Design • To decide upon a plan for change in the world that, when realized, satisfies stakeholders

Design problem and solution design problem design solution

Design project design problem design solution design project

Design cycle synthesize analyze evaluate

Design cycle synthesize goals constraints assumptions decisions ideas analyze evaluate

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

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

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

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

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

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

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

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

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

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

Design cycle at the micro level: design work synthesize goals constraints assumptions decisions ideas analyze evaluate

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 • …

Opportunistic versus rationalistic design work unexplored idea current decision explored idea

Mixed opportunistic and rationalistic design work unexplored idea current decision explored idea

Backtracking unexplored idea previous decision current decision explored idea

Simultaneous exploration unexplored idea current decision explored idea

Design cycle at the macro level: design process synthesize goals constraints assumptions decisions ideas analyze evaluate

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

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?

Waterfall requirements phase design phase implementation phase testing phase

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?

Agile • Our highest priority is to satisfy the customerthrough 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.

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?

Other life cycle models • Extreme programming • Rapid prototyping • Spiral model • Iterative development • Rational unified process • Synchronize-and-stabilize • …

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

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

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?

Choosing design methods to apply • Focus on essence • Focus on the unknown • Focus on making progress

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

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

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

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?

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?

Minimize backtracking what is it to accomplish? • Strive to minimize backtracking more than absolutely necessary • Strive to minimize backtracking later than absolutely necessary 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?

Routine, adaptive, and original design projects high original adaptive complexity routine low high low familiarity

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

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)

Informatics 121 Software Design I