Informatics 121 Software Design I
37
Department of Informatics, UC Irvine SDCL Collaboration Laboratory Software Design and sdcl.ics.uci.edu 1 Informatics 121 Software Design I Lecture 4 Duplication of course material for any commercial purpose without the explicit written permission of the professor is prohibited.
description
Informatics 121 Software Design I. Lecture 4 Duplication of course material for any commercial purpose without the explicit written permission of the professor is prohibited. Today’s lecture. Design is difficult. Informatics 121 definition. - PowerPoint PPT Presentation
Transcript of Informatics 121 Software Design I
Department of Informatics, UC IrvineSDCL Collaboration LaboratorySoftware Design and
sdcl.ics.uci.edu 1
Informatics 121Software Design I
Lecture 4
Duplication of course material for any commercial purpose without the explicit written permission of the professor is prohibited.
Department of Informatics, UC IrvineSDCL Collaboration LaboratorySoftware Design and
sdcl.ics.uci.edu 2
Today’s lecture
• Design is difficult
Department of Informatics, UC IrvineSDCL Collaboration LaboratorySoftware Design and
sdcl.ics.uci.edu 3
Informatics 121 definition
• To decide upon a plan for change in the world that, when realized, satisfies stakeholders
Department of Informatics, UC IrvineSDCL Collaboration LaboratorySoftware Design and
sdcl.ics.uci.edu 4
Design
designer plan
maker change in the world
audience experiences
other stakeholders
Department of Informatics, UC IrvineSDCL Collaboration LaboratorySoftware Design and
sdcl.ics.uci.edu 5
Design failures
Department of Informatics, UC IrvineSDCL Collaboration LaboratorySoftware Design and
sdcl.ics.uci.edu 6
Design failures
Department of Informatics, UC IrvineSDCL Collaboration LaboratorySoftware Design and
sdcl.ics.uci.edu 7
Design failures
(2006)
Department of Informatics, UC IrvineSDCL Collaboration LaboratorySoftware Design and
sdcl.ics.uci.edu 8
Design failures
(1988)
Department of Informatics, UC IrvineSDCL Collaboration LaboratorySoftware Design and
sdcl.ics.uci.edu 9
Design failures
(1988)
Department of Informatics, UC IrvineSDCL Collaboration LaboratorySoftware Design and
sdcl.ics.uci.edu 10
Design failures
(1988)
Department of Informatics, UC IrvineSDCL Collaboration LaboratorySoftware Design and
sdcl.ics.uci.edu 11
Design failures
(1988)
Department of Informatics, UC IrvineSDCL Collaboration LaboratorySoftware Design and
sdcl.ics.uci.edu 12
Design failures
(1979)
Department of Informatics, UC IrvineSDCL Collaboration LaboratorySoftware Design and
sdcl.ics.uci.edu 13
Design failures
(1984)
Department of Informatics, UC IrvineSDCL Collaboration LaboratorySoftware Design and
sdcl.ics.uci.edu 14
Design failures
(1940)
Department of Informatics, UC IrvineSDCL Collaboration LaboratorySoftware Design and
sdcl.ics.uci.edu 15
Design failures
Department of Informatics, UC IrvineSDCL Collaboration LaboratorySoftware Design and
sdcl.ics.uci.edu 16
Software design
software designer software
compiler runnable program
users experiences
other stakeholders
Department of Informatics, UC IrvineSDCL Collaboration LaboratorySoftware Design and
sdcl.ics.uci.edu 17
Design failures
Air-Traffic Control System in LA AirportIncident Date: 9/14/2004 Ironic Factor: ***** (IEEE Spectrum) -- It was an air traffic controller's worst nightmare. Without warning, on Tuesday, 14 September, at about 5 p.m. Pacific daylight time, air traffic controllers lost voice contact with 400 airplanes they were tracking over the southwestern United States. Planes started to head toward one another, something that occurs routinely under careful control of the air traffic controllers, who keep airplanes safely apart. But now the controllers had no way to redirect the planes' courses. ... The controllers lost contact with the planes when the main voice communications system shut down unexpectedly. To make matters worse, a backup system that was supposed to take over in such an event crashed within a minute after it was turned on. The outage disrupted about 800 flights across the country. ... Inside the control system unit is a countdown timer that ticks off time in milliseconds. The VCSU uses the timer as a pulse to send out periodic queries to the VSCS. It starts out at the highest possible number that the system's server and its software can handle—232. It's a number just over 4 billion milliseconds. When the counter reaches zero, the system runs out of ticks and can no longer time itself. So it shuts down. Counting down from 232 to zero in milliseconds takes just under 50 days. The FAA procedure of having a technician reboot the VSCS every 30 days resets the timer to 232 almost three weeks before it runs out of digits.
Department of Informatics, UC IrvineSDCL Collaboration LaboratorySoftware Design and
sdcl.ics.uci.edu 18
Design failures
NASA Mars Climate OrbiterIncident Date: 9/23/1999 Price Tag: $125 million Ironic Factor: **** WASHINGTON (AP) -- For nine months, the Mars Climate Orbiter was speeding through space and speaking to NASA in metric. But the engineers on the ground were replying in non-metric English. It was a mathematical mismatch that was not caught until after the $125-million spacecraft, a key part of NASA's Mars exploration program, was sent crashing too low and too fast into the Martian atmosphere. The craft has not been heard from since. ... Noel Henners of Lockheed Martin Astronautics, the prime contractor for the Mars craft, said at a news conference it was up to his company's engineers to assure the metric systems used in one computer program were compatible with the English system used in another program. The simple conversion check was not done, he said.
Department of Informatics, UC IrvineSDCL Collaboration LaboratorySoftware Design and
sdcl.ics.uci.edu 19
Design failures
Ariane 5 ExplosionIncident Date: 9/1997 Price Tag: $500 million Ironic Factor: **** (By James Gleick) It took the European Space Agency 10 years and $7 billion to produce Ariane 5, a giant rocket capable of hurling a pair of three-ton satellites into orbit with each launch and intended to give Europe overwhelming supremacy in the commercial space business.
All it took to explode that rocket less than a minute into its maiden voyage last June, scattering fiery rubble across the mangrove swamps of French Guiana, was a small computer program trying to stuff a 64-bit number into a 16-bit space.
...
This shutdown occurred 36.7 seconds after launch, when the guidance system's own computer tried to convert one piece of data -- the sideways velocity of the rocket -- from a 64-bit format to a 16-bit format. The number was too big, and an overflow error resulted. When the guidance system shut down, it passed control to an identical, redundant unit, which was there to provide backup in case of just such a failure. But the second unit had failed in the identical manner a few milliseconds before. And why not? It was running the same software.
Department of Informatics, UC IrvineSDCL Collaboration LaboratorySoftware Design and
sdcl.ics.uci.edu 20
Design failures
Department of Informatics, UC IrvineSDCL Collaboration LaboratorySoftware Design and
sdcl.ics.uci.edu 21
Design failures
Department of Informatics, UC IrvineSDCL Collaboration LaboratorySoftware Design and
sdcl.ics.uci.edu 22
Design failures
Department of Informatics, UC IrvineSDCL Collaboration LaboratorySoftware Design and
sdcl.ics.uci.edu 23
A caveat: not all design failures are bad
Department of Informatics, UC IrvineSDCL Collaboration LaboratorySoftware Design and
sdcl.ics.uci.edu 24
A caveat: not all design failures are bad
But we generally do not have this luxury!
Department of Informatics, UC IrvineSDCL Collaboration LaboratorySoftware Design and
sdcl.ics.uci.edu 25
Design failures
designer plan
maker change in the world
audience experiences
other stakeholders
Department of Informatics, UC IrvineSDCL Collaboration LaboratorySoftware Design and
sdcl.ics.uci.edu 26
Design failures
designer plan
maker
audience experiences
other stakeholders
feasibility
change in the world
Department of Informatics, UC IrvineSDCL Collaboration LaboratorySoftware Design and
sdcl.ics.uci.edu 27
Design failures
designer plan
maker change in the world
audience
other stakeholders
desirability
experiences
Department of Informatics, UC IrvineSDCL Collaboration LaboratorySoftware Design and
sdcl.ics.uci.edu 28
Design failures
designer plan
maker
audience
other stakeholders
desirability
experiences
feasibility
change in the world
Department of Informatics, UC IrvineSDCL Collaboration LaboratorySoftware Design and
sdcl.ics.uci.edu 29
Detour: wicked problems
• 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
Department of Informatics, UC IrvineSDCL Collaboration LaboratorySoftware Design and
sdcl.ics.uci.edu 30
Difficulty #1: problem, solution, change
• The understanding of a design problem goes hand-in-hand with the understanding of its design solution
• This understanding may well change, sometimes dramatically so, during the design project
• The challenge is to anticipate this volatility and identify and focus on the essence of the design problem at hand
Department of Informatics, UC IrvineSDCL Collaboration LaboratorySoftware Design and
sdcl.ics.uci.edu 31
Difficulty #2: success, failure, tradeoffs
• A design’s success is not absolute, but judged relative to other possible designs that could have been made
• A designer must deal with tradeoffs all the time, and cannot make all stakeholders equally satisfied with the change in the world
• The challenge is to identify and address key tradeoffs early
Department of Informatics, UC IrvineSDCL Collaboration LaboratorySoftware Design and
sdcl.ics.uci.edu 32
Difficulty #3: quality, cost, time
• There is no optimal solution to a design problem, designers must find a solution that is good enough
• The challenge is to find key quality and cost considerations early
Department of Informatics, UC IrvineSDCL Collaboration LaboratorySoftware Design and
sdcl.ics.uci.edu 33
Difficulty #4: longevity
• A change in the world may last for a very long time…
• …and may well need to accommodate future changes in the world
• The challenge is to identify and balance present needs with future possibilities
Department of Informatics, UC IrvineSDCL Collaboration LaboratorySoftware Design and
sdcl.ics.uci.edu 34
Routine, adaptive, original design
Department of Informatics, UC IrvineSDCL Collaboration LaboratorySoftware Design and
sdcl.ics.uci.edu 35
Design work
• Goal driven• People oriented• Fluid• Creative• Rigorous• Knowledge intensive• Uncertain• Subjective
Department of Informatics, UC IrvineSDCL Collaboration LaboratorySoftware Design and
sdcl.ics.uci.edu 36
Design studio 1
• You are tasked with designing a “virtual campus visit” system that is to advertise UC Irvine and the wonderful things that are going on here
• Identify the different audiences and what their experiences should be
• Identify the other stakeholders and the goals they may have
• Clearly document these in a typewritten document, to be handed in on Monday, October 15, at the beginning of class– separate list of audience and experiences– separate list of other stakeholders and goals
Department of Informatics, UC IrvineSDCL Collaboration LaboratorySoftware Design and
sdcl.ics.uci.edu 37
Design studio 1
• Assignment is on an individual basis, but will be continued in class on Monday
• You should identify as broad an audience and experiences as possible
• You should identify as broad a range of other stakeholders and goals as possible
• The overall focus is on brainstorming– your document does not need to have lengthy narratives (but should
be clear)
