1. Agenda – week 8 6:00 – 6:10 Questions, announcements, intro
6:10 – 6:50
Activity: estimation exercise
6:50 – 7:30
Lecture: ATAM
7:30 – 7:40
Break
7:40 – 8:30
Activity: practice parts of ATAM
8:30 – 8:40
8:40 – 9:10
ATAM activity continues
9:10 – 9:20
Assignment 8-1
9:20
Wrap-up

2. Estimation exercise What is the bandwidth of an 18-wheeler?
(“bandwidth” = total data/total time)
Assume a truck can go from Columbus to New York in 12 hr
Its cargo area is 53 ft x 8 ft x 10 ft
Pick a storage medium
Estimate the Columbus-New York bandwidth, using this truck and your medium
Include media creation time
Include loading and unloading time
Include drive time
Express your answer in MB/sec

3. Design problem - ATAM
Review architectural decisions for a voting system to achieve the given scenarios
Revise if you want to (add or change decisions, add or change scenarios)
Rate scenarios H/M/L for importance
Rate scenarios H/M/L for difficulty
Report your ratings on the whiteboard
Break
Analyze architectural decisions with respect to the top-rated scenarios (details on next slide: Analysis Steps)

4. Analysis steps (see also pp 282-283 and example on pp 297-299)
Identify decisions with sensitivity; check Helps and/or Harms column
Make a second pass and check any decisions that are tradeoffs (help one scenario, harm another)
For each “Harms” checkmark, decide if the decision is a risk or not
(see also pp and example on pp )

5. Architectural decisions for voting system
Voting devices will be PCs with touch-sensitive displays (assume $400/ touch-sensitive monitor)
Votes will be recorded in an open source relational DBMS
Sign-in tables will be equipped with PCs and electronic signature capture pads
All PCs at polling places will run Linux (assume $800/PC and $200/non-touch-sensitive monitor)
All PCs at a polling place will be connected to a 100 Mbit LAN

6. More decisions for voting system
Polling place LANs will be isolated from the public internet
The sign-in table PCs will have software than can do post-election vote collection and reporting
Vote reporting will use an encrypted channel over a dialup connection
Each voting PC will be equipped with a standard GUI and a large-print GUI to support visually-impaired voters

7. QAS: Accuracy (S1) Source of stimulus Person Stimulus Request to vote
Artifact
Access control
Environment
Normal operation
Response
One-person-one-vote maintained
Response measure
Request granted if and only if the person is a registered voter who has not voted in this election already

8. QAS: Security (S2) Source of stimulus Person or program Stimulus
Attempt to read a voter’s votes
Artifact
Vote recording subsystem
Environment
Normal operation
Response
Confidentiality maintained
Response measure
Attempt blocked and recorded

9. QAS: Availability (S3) Source Murphy’s Law Stimulus Software crash
Artifact
Voting device
Environment
Normal operation
Response
Voting continues
Response measure
Votes previously cast on the failed device are included in final tally, and with 99.99% probability, voter can vote anyway

10. QAS: Capacity (S4) Source Registered voters Stimulus
Voters arrive at a rate of 1/min
Artifact
Polling place
Environment
Normal operation
Response
Reasonable lines
Response measure
Average wait time to vote no more than 30 min (assume this requires at least 4 working voting devices and at least 2 working sign-in stations)

11. QAS: Accessibility (S5)
Source
Vision problems
Stimulus
A visually impaired person wants to vote
Artifact
Voting device
Environment
Normal operation
Response
Successful voting
Response measure
The voter signs in, discovers the candidates and issues, and votes, by means that do not require vision

12. QAS: Cost (S6) Source Customer Stimulus Equipment order Artifact
System pricing
Environment
Sales
Response
System is affordable
Response measure
Cost of voting devices, support equipment and software licenses for a polling place must not exceed $20,000

13. Scenario sheet for ATAM
Scenario notes: Id
Import.
Diff. S1
Decision
Helps
Harms
Trade?
Risk?

14. Scenario sheet for ATAM
Scenario notes: Id
Import.
Diff. S2
Decision
Helps
Harms
Trade?
Risk?

15. Scenario sheet for ATAM
Scenario notes: Id
Import.
Diff. S3
Decision
Helps
Harms
Trade?
Risk?

16. Scenario sheet for ATAM
Scenario notes: Id
Import.
Diff. S4
Decision
Helps
Harms
Trade?
Risk?

17. Scenario sheet for ATAM
Scenario notes: Id
Import.
Diff. S5
Decision
Helps
Harms
Trade?
Risk?

18. Scenario sheet for ATAM
Scenario notes: Id
Import.
Diff. S6
Decision
Helps
Harms
Trade?
Risk?

19. Scenario sheet for ATAM
Scenario notes: Id
Import.
Diff.
Decision
Helps
Harms
Trade?
Risk?

20. Scenario sheet for ATAM
Scenario notes: Id
Import.
Diff.
Decision
Helps
Harms
Trade?
Risk?