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

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

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)

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 282-283 and example on pp 297-299)

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

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

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

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

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

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)

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

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

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

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

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

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

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

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

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

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