# Glossary
**DID** Decentralized Identifier (W3C standard). DIDs are string identifiers which can be resolved to obtain a DID document and document metadata.
**dDID** see downstream DID
**downstream DID** A DID whose document metadata contains a signature from an upstream entity attesting to the validity of the information contained in the corresponding DID document.
**DID document** A file containing data pertaining to the DID subject, such as their public keys (or other verification material) and/or service endpoints.
**DID document metadata** A file containing metadata pertaining to the corresponding DID document.
**DID subject** The individual or legal entity to which a DID refers.
**DID controller** An individual or legal entity who holds the update secret for a DID.
**upstream entity** The subject of an upstream DID.
**upstream entity** The subject of a downstream DID.
**update commitment**
**update secret**
**recovery commitment**
**recovery secret**
**root DID**
**root event date**
**root event time**
**service**
**service endpoint**