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Review and revise architectural decisions for a voting system, rate scenarios, analyze with ATAM method. Dive into decisions' sensitivity, trade-offs, and risks for a robust system.
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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 • 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