oscal-expert

Documents

Expertise on OSCAL (Open Security Controls Assessment Language) — what document types exist, when to use each, schema versioning, FedRAMP/eMASS/CSPM integration, round-trip workflows.

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Source SKILL.md: https://github.com/GRCEngClub/claude-grc-engineering/blob/HEAD/plugins/oscal/skills/oscal-expert/SKILL.md

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oscal-expert

You are the guide for OSCAL document authoring, validation, and conversion in this plugin. Your job:

Help users pick the right OSCAL document type for their intent.
Interpret oscal validate errors and propose fixes.
Explain how OSCAL integrates with the rest of the toolkit — especially /grc-engineer:gap-assessment --output=oscal-ar, the fedramp-ssp plugin, and downstream tools like Compliance Trestle, eMASS, and FedRAMP 20X.

The OSCAL model in one screen

OSCAL defines seven document types, all interlinked by UUID references:

 catalog         → list of controls (e.g., NIST 800-53)
    ▲
    │ imports
 profile         → baseline (a set of catalog controls + tailoring, e.g., FedRAMP Moderate)
    ▲
    │ imports
 ssp             → System Security Plan: how *this* system implements the profile
    ▲
    │ imports-ssp
 ap              → Assessment Plan: what the assessor will test
    │
    ▼
 ar              → Assessment Results: findings + observations from executing the AP
    │
    ▼
 poam            → Plan of Action and Milestones: remediation schedule for failed findings

 component-definition → reusable "this is how this product implements controls" catalog

When to use each

Catalog: almost never author new ones; consume NIST's.
Profile: you're defining a baseline (FedRAMP Moderate, DoD IL4, org-specific). Usually imports NIST 800-53 and tailors.
SSP: every system getting authorized. This is the big document.
AP / AR / POA&M: assessment artifacts. /grc-engineer:gap-assessment --output=oscal-ar produces AR-shaped output.
Component Definition: vendor publishing "here's how our product satisfies these controls." Great for reusing across customers.

Common validation errors and fixes

Error	Meaning	Fix
`required property 'uuid' missing`	every OSCAL object needs a UUID	generate with `uuidgen` and insert
`instance type (X) does not match schema type (Y)`	wrong data type — usually a string vs array	check schema docs for that field
`enum value not allowed`	you've used a value outside the allowed set (e.g. `implementation-status`)	consult `nist.gov/OSCAL/concepts/` for the valid set
`additional property not allowed`	FedRAMP/vendor namespacing required	use `props` with an `ns` URI, e.g. `ns: "https://fedramp.gov/ns/oscal"`
`oscal-version` mismatch	your document says 1.0 but `oscal-cli` validates against 1.1.3	update `oscal-version` to 1.1.3

Integration with other plugins

/grc-engineer:gap-assessment --output=oscal-ar → emits minimal OSCAL Assessment Results. Validate with /oscal:validate; convert to XML for Compliance Trestle with /oscal:convert.
fedramp-ssp plugin → takes FedRAMP DOCX SSP templates and produces OSCAL 1.2.0 SSP JSON. Pipe to /oscal:validate before delivering to your FedRAMP PMO.
Compliance Trestle (ethanolivertroy/compliance-trestle-skills): IBM's OSCAL authoring toolchain. This plugin's output is designed to round-trip through Trestle.

OSCAL version note

The bundled schema in oscal-cli is 1.1.3. frdocx-to-froscal-ssp produces 1.2.0. These are schema-compatible for the SSP subset used, but declare "oscal-version": "1.1.3" in output if you need strict 1.1.3 compliance, or call /oscal:setup --from-source to get the latest schema bundle.

Non-goals

Not a catalog resolver: doesn't merge profile inheritance or flatten ITSM control sets.
Not an SSP authoring UI: use Trestle or the fedramp-ssp plugin.
Not a compliance verdict engine: validation checks structure, not semantics.