CS-314, Spring 2016
Design Studio 7. Safety - Wednesday, May 4, 2016

Pre-class work and Pre-Quiz, In-class work, and Post-class work for DS7.

The design studio pre-class work is individual. The design studio pre-Quiz is an individual quiz.

Pre-Quiz DUE Thursday 14 April 2016, 11:55 PM

CREDIT: Pre-Quiz: 10 points, Design Studio: 10 points

Design Studio User Story: As a student in CS 314, I want to understand the role of software engineering principles in safety so that I can design and build software that satisfies safety requirements.

1. Students understand how to analyze a safety incident report in order to identify specific things that caused the problem.
2. Students understand what software engineering principles were involved in causing the problem.
3. Students can propose how software engineering principles should have been applied, and changes that would have avoided the problem.

Pre-work and Pre-Quiz User Stories:

As a student in CS 314, I want to:

• be able to analyze existing documentation of prior software safety incidents, spcifically those involved in the Therac-25 so that I can identify critical design and development principles that affect safety.
• be able to identify specific architectural and design changes that can mitigate prior incidents so that I can address safety issues.
• identify processes and principles I have learned that can help satisfy safety requirements so that I can use them in my career.

In-class activity User Stories:

As a student in CS 314, I want to:

• practice incident analysis and propose changes to a specific system to satisfy safety requirements so that I can apply these skills when I need to.

Post-class work User Stories:

• As a student in CS 314, I want to personally assess my learning from the pre-work and in-class activity so that I can relate it to things I already know and use it in my career.

Design Studio Pre-Class work - Do This Before Class, Quiz due Tuesday night 11:55 pm

Description:

The pre-work consists of studying the Therac-25 incident reports. The full report is contained in Medical Devices: The Therac-25 by Nancy Leveson and is available in this PDF. The most relevant portions of the report for this design studio are the descriptions of the Tyler and Yakima accidents on pages 25-28 and 35-38. In addition, Dr. Bieman prepared some slides that give some background about the overall hardware and software system. These can be found in DS7SafetyTherac25Slides.pdf.

Tasks:

1. Complete the pre-class reading:

• Skim the full report as needed to gain an overview of the Therac-25, its use, and the safety incidents.
• Study the report excerpt.

2. Complete the pre-class preparation:

• The in-class work is to answer the following questions, so look for evidence in the report and think about how you will answer these questions.
  • What is the role of shared variables in causing the Tyler accidents (Section 3.5)?
  • What is the role of shared variables in causing the Yakima accidents (Section 3.6)?
  • What is wrong with the relationship between the user interface software and the rest of the Therac-25 software?
  • How would you modify the software architecture, in particular the connection between the user interface and the functional parts of the system? Describe an alternative design.
  • How could agile software development processes (e.g. extreme programming or SCRUM), be used to develop embedded software used to control medical devices while ensuring safety requirements are met?

3. Take the Safety Quiz, available in Canvas.

Grading:

1. You will receive an individual quiz grade for the pre-quiz.

Design Studio In-Class Activity - Work in your Team

TEAM WORK

Description:

You must answer the questions shown above in the pre-class preparation description. Follow the instructions for Task 1 in DS7-InClass.pdf.

What you need to do:

1. With your team, work through Task 1, and record you work on the Results Sheet to turn in at the end of class.

2. Turn in your Results Sheet at the end of class.

Grading:

The team portion of your DS7 grade (5 points) will be based on your result sheet.

Design Studio Post-Class work - Do This After Class

INDIVIDUAL WORK

Post-class retrospective writing DUE Thursday 5 May 2016, 11:55 PM

Description:

You need to write a self-learning assessment for the in-class activity. Follow the instructions for Task 2 in DS7-InClass.pdf.

What you need to do:

1. Write your assessment and submit it via Canvas. Make sure your name is included in your file or it will not be graded and you will receive a 0. If your submission is not a pdf file or a cut/paste into the Canvas text box, or if it is longer than 1 page it will not be graded and you will receive a 0.

Grading:

The individual portion of your DS7 grade (5 points) will be based on how thoughtfully you have addressed the problem in Task 2, and also on how well you have constructed your writing (paragraphs and arguments).

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