lec1 - Design and Analysis of Information Systems Michael...

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Unformatted text preview: Design and Analysis of Information Systems Michael Gruninger Semantic Technologies Lab University of Toronto September 7, 2010 Gruninger (MIE350) Design and Analysis of Information Systems September 7, 2010 1 / 21 Engineering Design Almost every engineering discipline has a design and analysis course Mechanical Civil Electrical Chemical Gruninger (MIE350) Design and Analysis of Information Systems September 7, 2010 2 / 21 Motivation We are immersed in software Software applications are being embedded within business systems, mechanical devices, and electrical systems. We need to efficiently design and implement reliable software for complex systems. Gruninger (MIE350) Design and Analysis of Information Systems September 7, 2010 3 / 21 Space Shuttle Four identical machines, running identical software, pull information from thousands of sensors, make hundreds of milli-second decisions, vote on every decision, check with each other 250 times a second. A fifth computer, with different software, stands by to take control should the other four malfunction. The software is responsible for I giving the orders to gimbal the main engines, executing the dramatic belly roll the shuttle does soon after it clears the tower. I throttling the engines to make sure the craft doesnt accelerate too fast. I keeping track of where the shuttle is, ordering the solid rocket boosters to fall away, making minor course corrections I shutting down main engines when the shuttle is in correct position in orbit Gruninger (MIE350) Design and Analysis of Information Systems September 7, 2010 4 / 21 Space Shuttle: Design Failures The two catastrophic shuttle accidents were due to mechanical design faults. The shuttle software is practically bug-free: the last three versions of the program each 420,000 lines long had just one error each. The last 11 versions of this software had a total of 17 errors. Commercial programs of equivalent complexity would have 5,000 errors. Gruninger (MIE350) Design and Analysis of Information Systems September 7, 2010 5 / 21 Space Shuttle Software: Methodology At the on-board shuttle group, about one-third of the process of writing software happens before anyone writes a line of code. NASA and the Lockheed Martin group agree in the most minute detail about everything the new code is supposed to do and they commit that understanding to paper, with the kind of specificity and precision usually found in blueprints. Nothing in the specs is changed without agreement and understanding from both sides....
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This note was uploaded on 09/20/2011 for the course MIE 350 taught by Professor M.gruninger during the Fall '10 term at University of Toronto- Toronto.

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lec1 - Design and Analysis of Information Systems Michael...

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