The core metadata bootstrap sources, by entity type, are:
releases: Crossref metadata, with DOIs as the primary identifier, and PubMed (central), Wikidata, and CORE identifiers cross-referenced
containers: munged metadata from the DOAJ, ROAD, and Norwegian journal list, with ISSN-Ls as the primary identifier. ISSN provides an "ISSN to ISSN-L" mapping to normalize electronic and print ISSN numbers.
creators: ORCID metadata and identifier.
file metadata and matches (file-to-release) come from earlier
Internet Archive matching efforts, and in particular efforts to extra
bibliographic metadata from PDFs (using GROBID) and fuzzy match (with
conservative settings) to Crossref metadata.
The intent is to continuously ingest and merge metadata from a small number of large (~2-3 million more more records) general-purpose aggregators and catalogs in a centralized fashion, using bots, and then support volunteers and organizations in writing bots to merge high-quality metadata from field or institution-specific catalogs.
Progeny information (where the metadata comes from, or who "makes specific claims") is stored in edit metadata in the data model. Value-level attribution can be achieved by looking at the full edit history for an entity as a series of patches.