Arc Skills / Requirements

Compare child requirements to parent requirements

Arc Skills compares parent clauses with their recorded child requirements at named revisions. The result shows covered, partial, and unsupported obligations without treating a derives link as proof.

Use this skill

Use Arc Skills to compare the supplied child requirements with their parent.

Inputs:
- Exact parent and child statements, IDs, and revisions
- Recorded derivation links, allocations, modes, and definitions
- Any independent sources for child limits or added behavior

Return a parent-clause coverage map and a list of child obligations without an established source.
Compare actors, triggers, modes, and numerical bounds exactly; preserve all original wording

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What you provide and what you get

Inputs and outputs
What you have	How it is used	What you get
Parent baseline	Splits the promised outcome into conditions and limits	Parent coverage map
Child baseline and links	Shows actual derived obligations and revisions	Coverage or mismatch verdict
Alternate sources	Justifies details beyond the parent	Open approval question

A five-second display child under a two-second report parent

Illustrative engineering example.

The parent requires Controller reporting after fault detection; the only child governs a Display after message receipt. Both are current in the illustrative input.

P-4 rev B: The Controller shall report a fault within 2 s of detection.
C-7 rev A: The Display shall show fault status within 5 s of receiving a Controller message.
Recorded relation: P-4 derives C-7.

A five-second display child under a two-second report parent — illustrative output
Parent clause / child	Coverage	Reason and action
Controller reports fault	Uncovered by C-7	Display behavior begins after message receipt; find or derive Controller reporting duty.
Within 2 s of detection	Uncovered by C-7	C-7 permits 5 s after a later event; it cannot prove the parent limit.
C-7 display within 5 s	Child addition	Useful downstream behavior perhaps, but needs its own source or approved design decision.

The derives relationship records intent to link P-4 and C-7, but the actor and timing reference change. Even perfect compliance with C-7 can leave P-4 violated, so the child set is insufficient for the declared parent scope.

A Controller transmission child might address the first gap. It still needs a timing allocation that fits the 2 s end-to-end limit. The 5 s display limit should not be deleted automatically; its separate origin needs tracing.

Compare obligations rather than titles

Pin parent and child revisions and confirm link direction.
Decompose the parent into actor, event, response, mode, and limit.
Map each child only to clauses it actually establishes; compare bounds mathematically.
List every additional child obligation and its independent source or unresolved decision.

Questions about this task

Does a stricter child always cover a parent?

Only when actor, trigger, scope, and measured outcome also align. A faster display is not the same as a faster Controller report.

Should the child be rewritten immediately?

First locate the original timing allocation or stakeholder source. Proposals remain separate from controlled baseline text.

Sources and further reading

NASA Systems Engineering Handbook: Lifecycle and requirements guidance; the example decisions are illustrative.