Editing Non-Functional Requirements (section)

== 5. Maintainability ==

<span id="nfr-main-01-three-tier-separation"></span>
=== NFR-MAIN-01 — Three-tier separation ===

'''Requirement:''' No SQL shall appear outside <code>primes.cbl</code>. No file I/O (other than console DISPLAY) shall appear outside <code>primesui.cbl</code>.<br />
'''Rationale:''' Tier separation is the principal architectural rule of this system; violating it makes changes to one tier affect others.<br />
'''Test approach:''' Grep all <code>.cbl</code> files for EXEC SQL and for SELECT/WRITE file statements; verify only the expected programs contain them.<br />
'''Priority:''' Must Have<br />
'''Source:''' Architecture design principle; observed and partially met (primesgen has an unused FD declaration — minor violation).<br />
'''Status:''' Partially met.

<span id="nfr-main-02-copybook-as-interface-contract"></span>
=== NFR-MAIN-02 — Copybook as interface contract ===

'''Requirement:''' Changes to any copybook must be reviewed for impact on all programs that COPY it before the change is applied.<br />
'''Rationale:''' Copybooks are shared; a field-size change in a copybook breaks every program that uses it without any compile-time warning in all cases.<br />
'''Test approach:''' Impact analysis process; verified by recompiling all programs after any copybook change.<br />
'''Priority:''' Must Have<br />
'''Source:''' Standard COBOL maintenance practice<br />
'''Status:''' [CONFIRMED as a process requirement — no tooling enforcement in place]

<span id="nfr-main-03-code-commentary"></span>
=== NFR-MAIN-03 — Code commentary ===

'''Requirement:''' Every paragraph shall carry a comment line stating its purpose. Every EXEC SQL block shall carry a comment stating what it does and why.<br />
'''Rationale:''' Current source has minimal commentary; future maintainers depend on the specification documents, which is insufficient.<br />
'''Test approach:''' Code review checklist.<br />
'''Priority:''' Should Have<br />
'''Source:''' COBOL coding best practice<br />
'''Status:''' '''NOT MET''' in current source.

<span id="nfr-main-04-testability"></span>
=== NFR-MAIN-04 — Testability ===

'''Requirement:''' Each tier (primesgen, primes, primesui) shall be callable in isolation with a synthetic control block, without requiring the full three-tier stack.<br />
'''Rationale:''' Unit testing individual tiers is only possible if they can be called with a test harness.<br />
'''Test approach:''' Write a minimal test driver for each program; verify it compiles and runs independently.<br />
'''Priority:''' Should Have<br />
'''Source:''' Testability principle; the method-dispatch pattern makes this achievable by design.<br />
'''Status:''' [UNCONFIRMED — no test harnesses exist]


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<span id="portability-and-compatibility"></span>