# concept-graph
The materialized hierarchy of a code system.
Integer-keyed compressed sparse row adjacency for a code system's is-a
hierarchy and each typed relationship, plus roaring transitive-closure bitmaps.
Subsumption is a bitmap membership test, and the ECL evaluator compiles
constraints to set algebra over these bitmaps. The graph is built offline by a
loader and served read-only; no request traverses edges live. No FHIR or SNOMED
specification governs the layout: it is this project's own design.
## Where it sits
`concept-graph` is one crate of [FerroTERM](https://github.com/rubentalstra/FerroTERM),
a pure-Rust FHIR terminology server for SNOMED CT, LOINC, and other clinical
code systems. The crates are published so other projects can reuse them; the
API is pre-1.0 and moves with the FerroTERM release train. Documentation:
<https://docs.rs/concept-graph>.
## Licence
Business Source License 1.1 (`LICENSE`): free to read, build, modify, and
redistribute, free for non-production use and for non-commercial production
use; commercial production use needs a licence from the Licensor; each version
becomes Apache License 2.0 four years after it is published. Clinical terminology content (SNOMED
CT, LOINC, RxNorm, ICD, the Dutch national code systems) is licensed by its
publisher and is never part of this crate.