Everything Else

Release comparison, artefact inspection, performance benchmarks, layered builds, and the full command reference.

Release Comparison `experimental` :lucide-test-tube

Compare two NDJSON artefacts to see what changed between SNOMED releases.

sct diff --old snomed-uk-20240901.ndjson \
         --new snomed-uk-20250301.ndjson \
         --format text

Reports:

Concepts added
Concepts inactivated
Terms changed (preferred term or FSN updated)
Hierarchy changed (concept moved in IS-A tree)

# Machine-readable NDJSON output for scripting
sct diff --old old.ndjson --new new.ndjson --format ndjson | \
  jq 'select(.change_type == "term_changed")'

Artefact Inspection `experimental!`

Inspect any sct-produced file without needing to know its internals.

sct info snomed.ndjson
sct info snomed.db
sct info snomed-embeddings.arrow

Output includes:

Concept count
Schema version
Hierarchy breakdown (concept counts per top-level hierarchy)
File size
Release date (if present)

Performance

All timings below are for the UK Monolith (837,930 active concepts) on NVMe SSD.

Operation	Time	Output size
RF2 → NDJSON	~52 s	1.3 GB
NDJSON → SQLite	~32 s	1.9 GB
NDJSON → Parquet	~6 s	785 MB
NDJSON → Markdown	~32 s	3.2 GB (837,930 files)
MCP server startup	< 5 ms (small db) / ~373 ms (full Monolith with TCT)	-

vs. remote FHIR terminology server (benchmark results):

Local SQLite queries are 50–2700× faster than equivalent FHIR R4 operations over the network. See benchmarks.md for full methodology and results.

Run the benchmarking suite yourself:

benchmarks/bench.sh \
  --server https://your-fhir-server/fhir \
  --db snomed.db \
  --runs 10 \
  --format table

UK Clinical Edition: Layered Builds

The UK SNOMED CT Clinical Edition is built by layering three RF2 releases:

sct ndjson \
  --rf2 SnomedCT_InternationalRF2_PRODUCTION_20250101T120000Z.zip \
  --rf2 SnomedCT_UKClinicalRF2_PRODUCTION_20250401T000001Z.zip \
  --rf2 SnomedCT_UKDrugRF2_PRODUCTION_20250401T000001Z.zip \
  --locale en-GB \
  --output snomed-uk-20250401.ndjson

Later --rf2 flags override earlier ones for the same concept. The --locale en-GB flag selects GB English preferred terms from the UK language reference set.

Command Reference Summary

Command	Description
`sct ndjson`	RF2 → canonical NDJSON (build once per release)
`sct sqlite`	NDJSON → SQLite + FTS5 (SQL + full-text search)
`sct tct`	Add transitive closure table to an existing SQLite database
`sct parquet`	NDJSON → Parquet (DuckDB / analytics)
`sct markdown`	NDJSON → Markdown files (RAG / file reading)
`sct embed`	NDJSON → Arrow embeddings (requires Ollama)
`sct mcp`	Stdio MCP server for Claude (wraps SQLite)
`sct lexical`	Keyword search via FTS5
`sct semantic`	Semantic search via cosine similarity
`sct diff`	Compare two NDJSON releases
`sct info`	Inspect any sct-produced artefact
`sct tui`	Terminal UI (in the default build)
`sct gui`	Browser UI (requires `--features gui`)
`sct completions`	Generate shell completion scripts
`sct codelist`	Build and validate code lists (alias: `sct valueset`)
`sct refset`	Browse reference sets loaded into the SQLite database
`sct lookup`	Look up a single concept by SCTID or CTV3 code
`sct ecl`	Evaluate an ECL expression (`expand`) or refactor SCTIDs into ECL (`compress`)
`sct diagram`	Draw a concept's definition, ancestors, or descendants (tree/DOT/Mermaid)
`sct fst`	Build and query an FST-backed lexical index (exact/prefix/fuzzy/word search)
`sct map`	Map codes between terminologies (SNOMED/Read v2/CTV3/ICD-10/OPCS-4)
`sct read2`	Import final Read v2 maps from NHS Data Migration TRUD item 9

Next Steps

sct trud - automated download from NHS TRUD API
sct serve - drop-in FHIR R4 terminology server backed by SQLite
sct codelist publish - publish back to OpenCodelists (coming)

See spec/roadmap.md for the full list of planned features.