This document attempts to communicate the concepts outlined in the Decentralized Identifier space by using specialized terms to discuss specific concepts. This terminology is included below and linked to throughout the document to aid the reader:

A specific type of distributed ledger technology (DLT) that stores ledger entries in blocks of transactions that are grouped together and hashed into a cryptographic chain. Because this type of DLT was introduced by Bitcoin, the term "blockchain" is sometimes used to refer specifically to the Bitcoin ledger.
Decentralized Identifier (DID)
A globally unique identifier that does not require a centralized registration authority because it is registered with distributed ledger technology or other form of decentralized network. The generic format of a DID is defined in this specification. A specific DID scheme is defined in a DID method specification.
Decentralized Identity Management
Identity Management based on decentralized identifiers. Decentralized Identity Management extends the identifier creation authority beyond the traditional roots of trust required by X.500 directory services, the Domain Name System, and most national ID systems.
DID Registry
A role a system performs to mediate the creation, verification, updating, and deactivation of Decentralized Identifiers. A DID Registry is a type of Verifiable Data Registry (see [[VC-DATA-MODEL]]).
Decentralized Public Key Infrastructure (DPKI)
Public key infrastructure based on decentralized identifiers and identity records (e.g., DID Documents) containing verifiable public key descriptions.
A person, organization, or thing whose DID is registered and maintained by a delegate because the dependent is not in a position to control the private keys. A dependent becomes an identity owner when the dependent takes control of the private keys.
DID Controller
The entity, or a group of entities, in control of a DID and/or DID Document. Note that the DID Controller may or may not include the DID Subject.
DID Document
A set of data that describes the subject of a DID, including mechanisms, such as public keys and pseudonymous biometrics, that the DID subject can use to authenticate itself and prove their association with the DID. A DID Document MAY also contain other attributes or claims describing the subject. These documents are graph-based data structures that are typically expressed using [[JSON-LD]], but may be expressed using other compatible graph-based data formats.
DID Fragment
The portion of a DID URL that follows the first hash sign character (#). A DID fragment uses the same syntax as a URI fragment. See Section .
DID Method
A definition of how a specific DID scheme can be implemented on a specific distributed ledger or network, including the precise method(s) by which DIDs are resolved and deactivated and DID Documents are written and updated.
DID Path
The portion of a DID URL that begins with and includes the first forward slash character (/). A DID path uses the identical syntax as a URI path. See Section .
DID Query
The portion of a DID URL that follows the first question mark character (?). A DID path uses the identical syntax as a URI path. See Section .
DID Subject
The DID Subject is the entity that the DID Document is about, i.e., it is the entity identified by the DID and described by the DID Document.
A DID plus an optional DID path, optional ? character followed by a DID query, and optional # character followed by a DID fragment.
DID Scheme
The formal syntax of a Decentralized Identifier. The generic DID scheme is defined in this specification. Separate DID method specifications define a specific DID scheme that works with that specific DID method.
Distributed Ledger (aka DLT)
A distributed database in which the various nodes use a consensus protocol to maintain a shared ledger in which each transaction is cryptographically signed and chained to the previous transaction
An entity who creates a DID and associated DID document for a dependent who does not yet have the capacity to control the private keys. The dependent must rely on the delegate to safeguard the private keys until the dependent can assume control as the DID subject.
Identity Owner
The natural person, party, organization, or thing whose identity is represented by a DID and who directly controls the private keys to control the DID Document. (Note: this specification avoids the term "user" since a DID subject is not always an individual person.)
JSON Pointer
JSON Pointer defines a string syntax for identifying a specific value within a JavaScript Object Notation (JSON) document as defined in [[RFC6901]]
Key Description
A JSON object contained inside a DID Document that contains all the metadata necessary to use a public key or verification key. A list of standard key descriptions is included in Appendix .
Service Endpoint
A network address at which a service operates on behalf of a DID subject. Examples of specific services include discovery services, social networks, file storage services, and verifiable claim repository services. Service endpoints may also be provided by a generalized data interchange protocol such as Extensible Data Interchange.
Universally Unique Identifier as specified by RFC 4122 .
Extensible Data Interchange (aka XDI)
A semantic graph format and semantic data interchange protocol defined by the OASIS XDI Technical Committee.
An identifier as defined by [[RFC3986]].