trestle-oscal-models

name	trestle-oscal-models
description	>- Use when this capability is needed.

OSCAL Model Types in Trestle

The 7 OSCAL Model Types

Model Type	CLI Name	Directory	Description
Catalog	catalog	catalogs/	Collection of security controls (e.g., NIST 800-53)
Profile	profile	profiles/	Selection and modification of controls from catalogs
Component Definition	component-definition	component-definitions/	How a component implements controls
System Security Plan	system-security-plan	system-security-plans/	Complete system security documentation
Assessment Plan	assessment-plan	assessment-plans/	Plan for assessing security controls
Assessment Results	assessment-results	assessment-results/	Results of security assessment
POA&M	plan-of-action-and-milestones	plan-of-action-and-milestones/	Remediation tracking

Model Relationships

Catalog (controls)
    ↓ imports
Profile (selects + modifies controls)
    ↓ resolved profile catalog
Component Definition (how components implement controls)
    ↓ combined
System Security Plan (complete system documentation)
    ↓ assessed by
Assessment Plan → Assessment Results → POA&M

The Catalog → Profile → SSP Chain

1. Catalog defines controls (e.g., NIST 800-53 has ~1000 controls)
2. Profile imports controls from catalogs/profiles, selects subset, modifies parameters
3. Resolved Profile Catalog is the effective set of controls after profile modifications
4. Component Definition describes how specific components address controls
5. SSP combines profile + component definitions into implementation documentation

Profile Imports

A profile can import from:

• One or more catalogs
• One or more other profiles
• A mix of catalogs and profiles

Each import selects specific controls and can modify parameters and add content.

Common OSCAL Fields

All models share:

• uuid - Unique identifier
• metadata - Title, version, last-modified, oscal-version, roles, parties
• back-matter - Resources, citations, attachments

File Formats

• JSON (default): .json
• YAML: .yaml or .yml
• Within one model directory, don't mix formats

Element Paths

Trestle uses dot-notation to address elements within models:

• catalog.metadata - The metadata of a catalog
• catalog.groups.*.controls.* - All controls in all groups
• catalog.groups.0.controls.3 - Specific control (0-indexed)

Rules:

• Paths are relative to the file being operated on
• Use * wildcard for arrays (quote on *nix shells)
• Array syntax can be skipped: catalog.controls.control = catalog.groups.controls.control

Trestle Operations on Models

Operation	Command	Description
Create	trestle create -t <type> -o <name>	Create bare-bones sample model
Import	trestle import -f <file> -o <name>	Import existing OSCAL file
Split	trestle split -f <file> -e <elements>	Decompose into sub-files
Merge	trestle merge -e <elements>	Reassemble split files
Describe	trestle describe -f <file> -e <element>	Inspect model structure
Validate	trestle validate -f <file> or -t <type> -n <name> or -a	Check model integrity
Assemble	trestle assemble <type> -n <name>	Combine split parts to dist/
Replicate	trestle replicate <type> -n <name> -o <new>	Copy/rename model

SSP Special Concepts

• This System component: Default component in every SSP (name: "This System")
• By-Component responses: Implementation prose organized by component
• Rules and Parameters: Embedded in component definition properties, propagated to SSP
• Implementation Status: Tracked per-component per-control
• Leveraged SSPs: Inheritance from provider systems

Persona Ownership

Each OSCAL model type has a primary owner persona responsible for authoring and maintaining it:

Model Type	Primary Persona	Trestle Commands	Notes
Catalog	Regulators	catalog-generate, catalog-assemble	Source of truth for controls
Profile	Compliance Officers / CISO	profile-generate, profile-assemble	Tailored baselines with org guidance
Component Definition (Service)	Control Providers (vendors)	csv-to-oscal-cd, component-generate/assemble	Maps controls to product rules
Component Definition (Validation)	Control Assessors (PVP vendors)	csv-to-oscal-cd (with Check_Id)	Maps rules to automated checks
System Security Plan	System Owners / CIO	ssp-generate, ssp-assemble	Combines profile + compdefs
Assessment Plan	Assessors / CISO	create, split, merge	Defines assessment scope
Assessment Results	Assessors / PVP tools	xccdf-result-to-oscal-ar, tanium-result-to-oscal-ar	Scan findings
POA&M	System Owners	create, split, merge	Remediation tracking

In real organizations, one person may fill multiple persona roles. The ownership mapping is logical (separation of duties), not necessarily physical (one person per artifact).

Component Definition: The Bridge Artifact

The component definition plays a unique bridging role in the OSCAL model chain. It connects regulatory controls (governance layer) to automated assessment (technical layer) through two distinct component types:

Layer 1 — Service Components (Control-to-Rule)

Service components declare which technology-specific rules implement a regulation control:

• Authored by product vendors and service providers
• Maps: Control (e.g., AC-2) --> Rule (e.g., rule-account-types) --> Parameter (e.g., timeout=15min)
• Created via CSV spreadsheet (csv-to-oscal-cd with Component_Type=Service)
• Prose responses added via markdown (component-generate / component-assemble)

Layer 2 — Validation Components (Rule-to-Check)

Validation components declare which PVP checks validate a rule:

• Authored by assessment tool vendors and compliance engineers
• Maps: Rule (e.g., rule-account-types) --> Check_Id (e.g., test_github.GitHubOrgs.test_members_is_not_empty)
• Created via CSV spreadsheet (csv-to-oscal-cd with Component_Type=Validation and Check_Id column)
• Consumed by C2P (Compliance-to-Policy) to bridge to runtime assessment

End-to-End Traceability

Together, the two layers create the full compliance automation chain:

Regulation Control (NIST AC-2)
    --> Service Rule (rule-account-types)
        --> Validation Check (test_github.GitHubOrgs.test_members)
            --> Assessment Result (pass/fail)
                --> Control Posture (satisfied/not-satisfied)

This traceability enables automated posture computation: given PVP results, map backward through component definitions to determine control-level compliance status.

For full pipeline details, see the trestle-compliance-pipeline skill.

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