Chapter 34 — Comparative project

Chapter 34 — Comparative project

Lesson map

Lesson 34 published. Map, example, EX100.

flowchart TD
  N0["Learning outcomes"]
  N1["34.1 Framing the comparison"]
  N2["34.2 Gathering evidence"]
  N3["34.3 Recommending with justification"]
  N4["Synthesis"]
  N0 --> N1 --> N2 --> N3 --> N4
  N4 --> EX["Worked example"]
  EX --> Q["Exercise EX100"]

Logical drawing

flowchart LR
  N0["Learning outcomes"]
  N1["34.1 Framing the comparison"]
  N2["34.2 Gathering evidence"]
  N3["34.3 Recommending with justification"]
  N4["Synthesis"]
  N0 --> N1 --> N2 --> N3 --> N4 --> Q["EX100"]

[Learning outcomes]
    |
    v
[34.1 Framing the comparison]
    |
    v
[34.2 Gathering evidence]
    |
    v
[34.3 Recommending with justification]
    |
    v
[Synthesis]
    |
    v
[Worked example] --> [Exercise EX100]

Learning outcomes

You will (1) compare design options against criteria; (2) gather evidence for each option; (3) recommend with justification.

34.1 Framing the comparison

The board asks whether the cooperative should keep its permissioned ledger or move vouchers to an ordinary database with signed audit logs. Sofia frames a comparison against agreed criteria: integrity of records, privacy, cost, operational burden on volunteers, member trust and ability to recover from errors. Each criterion has a weight agreed with the board before any option is scored, so the result cannot be tuned to favour a preferred answer. Framing the comparison carefully ensures the decision rests on the cooperative's priorities rather than on enthusiasm for any particular technology.

34.2 Gathering evidence

For each option Sofia gathers evidence: costs from hosting invoices, volunteer time from the operations log, integrity from reconciliation results, privacy from her data map and member trust from a short survey. The ledger scores higher on shared tamper evidence and member trust; the database scores higher on privacy, cost and ease of correcting errors. She cites NIST IR 8202's guidance that organisations should consider whether a blockchain is needed at all. Gathering evidence for both options fairly prevents the comparison from becoming a defence of the existing choice.

34.3 Recommending with justification

The weighted scores are close: 3.6 for the ledger and 3.4 for the database. Sofia tests sensitivity: if privacy's weight rises slightly, the database wins. She recommends keeping the ledger for now, because members value shared records, while reducing data on it further and reviewing the decision in two years. She presents the closeness openly so the board understands that the choice is a judgement, not an obvious answer. The board accepts the recommendation and records its reasoning, including the review date, in the decision records.

Worked example

Weighted scores of 3.6 for the ledger and 3.4 for the database lead Sofia to recommend keeping the ledger, with less data and a two-year review.

Synthetic case. The comparison and scores are synthetic; NIST IR 8202 is a real source.

Errors and limits

Setting weights after scoring lets a comparison be tuned to a preferred answer.

Exercises

• EX100 — Alternative option. What alternative to the ledger is compared? Rubric: 3 = an ordinary database with signed audit logs;; 2 = database;; 1 = public chain;; 0 = none.
• EX101 — Weighted scores. What weighted scores did the options receive? Rubric: 3 = 3.6 ledger, 3.4 database;; 2 = 3.6/3.4;; 1 = equal;; 0 = none.
• EX102 — Sensitivity result. What does the sensitivity test show? Rubric: 3 = a slightly higher privacy weight favours the database;; 2 = privacy shifts it;; 1 = no change;; 0 = none.

Synthesis

Fair evidence, pre-agreed weights and sensitivity testing support honest recommendations.

Continue studying — chapter 34 of 40

← Chapter 33 (draft) · Course chapter index · Chapter 35 (draft) →