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SSSOM

Created

What it is

Section titled “What it is”

SSSOM (Simple Standard for Sharing Ontological Mappings) is a metadata standard for ontology mappings. It defines how to attach provenance, confidence, authorship, and justification to each mapping — turning a bare “A maps to B” triple into an auditable crosswalk edge. Published by Matentzoglu et al. in Database (2022).

How it works

Section titled “How it works”

Every SSSOM mapping is a row with three core fields and a set of mandatory + optional metadata:

FieldRole
subject_idThe source entity (e.g., a NIST 800-53 control)
predicate_idThe relationship (typically a SKOS or OWL predicate — SSSOM is predicate-agnostic)
object_idThe target entity (e.g., an ISO 27001 control)
mapping_justificationMandatory — why this mapping was asserted (manual review, LLM, lexical match, etc.)
confidenceOptional — numeric score, 0.0–1.0
author_idOptional — who authored the mapping
mapping_dateOptional — when it was authored or reviewed
mapping_toolOptional — what tool produced it
predicate_modifierOptional — supports negation (“A is not equivalent to B”)

Why it matters for crosswalks

Section titled “Why it matters for crosswalks”

SSSOM fills the five gaps that make bare SKOS insufficient for compliance crosswalking: confidence scores, provenance, many-to-many support, negation, and authored-by-whom. Every mature ontology alignment ecosystem has converged on something SSSOM-shaped — it’s not exotic, it’s the baseline.

In Crosswalker

Section titled “In Crosswalker”

SSSOM is the candidate edge metadata model for Crosswalker ontology-to-ontology crosswalks specifically — that is, the edges between concepts in two structured ontologies (framework↔framework mappings, framework↔synthetic spine mappings, and transitive crosswalks derived through a pivot). The 04-10 foundation synthesis proposes committing to SSSOM’s metadata fields as the required provenance envelope on every such crosswalk edge, paired with the NIST IR 8477 set-theory relationships as the predicate_id vocabulary. The decision is tracked in the Foundation roadmap under edge semantics commitment.

For spine-derived mappings (see Challenge 06), SSSOM also supports chained provenance — a derived crosswalk can cite its component mappings and composition operator, which matters for audit-grade trust.

Section titled “Links”