Arc Skills / Requirements

Derive sub-requirements from a parent requirement

Arc Skills derives candidate child requirements from a controlled parent and system boundary. It supplies a coverage map and leaves unapproved performance allocations or new behavior as explicit decisions.

Use this skill

Use Arc Skills to derive the smallest justified child set for the supplied parent requirement.

Inputs:
- Exact parent ID, statement, revision, and allocated boundary
- System decomposition, operating modes, and existing children
- Approved definitions, interface facts, and performance budgets

Return provisional child statements, allocation candidates, and a parent-clause coverage map.
Do not invent duration, rate, or budget allocations. Keep unsupported engineering choices open and leave final IDs to the receiving system

Set up the toolkit · Read the skill instructions

What you provide and what you get

Inputs and outputs
What you have	How it is used	What you get
Parent requirement	Defines the two promised outcomes	Child coverage map
System decomposition	Locates storage and downlink owners	Allocation candidates
Existing children and definitions	Prevents duplicate children and invented triggers	Open assumptions

Separate storing from downlinking

Illustrative engineering example.

The parent has two independent responses. Storage is performed by Recorder; downlink is performed by Communications. No retention period or data rate is in the source.

P-9: The imaging subsystem shall store commanded images and downlink them on request.
Architecture: Recorder owns image storage; Communications owns downlink.
Existing child set: empty.

Separate storing from downlinking — illustrative output
Parent phrase	Provisional child statement / owner	Coverage and open term
Store commanded images	C-A: The Recorder shall store an image after a valid capture command. / Recorder	Covers storage; command validity needs definition.
Downlink them on request	C-B: The Communications subsystem shall downlink stored images after a valid downlink request. / Communications	Covers downlink; request validity needs definition.
Duration, rate, encryption	No child proposed	Not present in P-9; require separate approved source.

C-A and C-B are useful children because they have different actors and can be verified independently. The map covers both parent actions, provided the project confirms the trigger wording and the handoff between Recorder and Communications.

A derives link alone would not prove coverage. The child set deliberately omits retention time, throughput, and encryption because none is supplied; adding them would create new obligations.

Decompose by verifiable responsibility

Record the exact parent and existing children at known revisions.
Split only distinct outcomes that need separate ownership or evidence.
Preserve limits and modal conditions; never apportion an unsourced budget.
Map every parent phrase and list any added child intent with its source.

Questions about this task

Are local labels C-A and C-B final IDs?

No. They identify draft rows in this example; the receiving system generates its persistent identifiers.

What if one child can implement both outcomes?

Keep one child when one actor and one evidence route genuinely cover the combined obligation. Sentence length alone does not require a split.

Sources and further reading

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