What this entity is
The canonical name is NMDC biosample metadata resource. 1
The resource is maintained as nmdc.metadata, with nmdc_metadata reported as its underscore-form Hive alias. 1 Known aliases are nmdc.metadata and nmdc_metadata. 1 The audit did not report a stable external identifier for this resource. 1
NMDC refers here to the National Microbiome Data Collaborative of DOE-BER. 1
Key facts
nmdc.metadata is one of the genuine NMDC resources identified among 7 maintained resources represented by 20 NMDC-named database entries. 1 Its biosample universe contains exactly 16,640 samples in nmdc.metadata.biosample_set. 1 The resource uses the NMDC LinkML-based data model and its *_set schema. 1 Its latest reported Iceberg commit is dated 2026-05-20. 1
The audit contrasts this canonical NMDC resource with ncbi biosample, whose co-hosted mirror contains exactly 51,711,888 biosamples and 756,112,544 attribute rows. 1 This contrast identifies a scale-selection hazard: the canonical NMDC biosample universe has 16,640 samples, whereas the NCBI mirror has 51,711,888 biosamples. 1
The resource is located in the nmdc tenant, while related resources such as nmdc mags are located in the kbase tenant. 1 This supports the audit’s cross-tenant distinction: NMDC classifier and metabolomics tables use separate file_id namespaces and must be bridged through sample_id using omics_files_table, rather than joined directly by file identifier. 2
The audit found that catalog tables have no comments and database properties are empty, so resource currency and provenance are not adequately exposed at discovery. 1 The pitfalls document refines this concern by recommending live catalog and schema inspection, because namespace availability, schemas, permissions, and database contents can change. 2 The audit recommends surfacing the maximum Iceberg committed_at timestamp in discovery tooling so users can assess currency. 1
NMDC metadata analyses also require care with representation: abiotic_features stores unmeasured variables as 0.0 rather than NULL, so zeros should be converted to NaN before analysis. 2
Relations to the wider wiki
This resource is central to cross-tenant-data-bridging because the audit places genuine NMDC resources and NMDC-related derivatives across different tenants. 1
It also informs provenance-aware-resource-discovery because the audit distinguishes canonical NMDC data from the NCBI re-host and recommends exposing provenance and currency together. 1
The resource is documented in NMDC Context Audit and pitfalls. 1,2