Checksum

Content hashes calculated using SHA1. Checksum references are used by document-typed entities in Aleph to refer to raw data in the archive (e.g. the document from which the entity is extracted).

Unfortunately, this has some security implications: in order to avoid people getting access to documents for which they know the checksum, properties of this type are scrubbed when submitted via the normal API. Checksums can only be defined by uploading a document to be ingested.

Matchable types allow properties to be compared with each other in order to assess entity similarity.

Pivot types are a stronger form of matchable types and can be used to find similar entities based on simple value lookups.