Glossary

Working definitions for terms used across the research notes, directory, and methodology. Definitions are written to reflect usage in the field, not to provide legal, regulatory, or clinical guidance.

Blockchain: A distributed ledger in which records are grouped into sequentially linked blocks. Each block contains a cryptographic hash of the prior block, making retroactive alteration detectable. The term is often used loosely to include distributed ledger designs that do not use this exact structure.
Distributed ledger: A record system replicated across multiple participants rather than held by a single authoritative party. Participants may be permissioned or open. The shared state is maintained through a consensus mechanism that all participants run. Blockchain is one type of distributed ledger.
Smart contract: Code stored and executed on a distributed ledger that runs when specified conditions are met. In healthcare applications, smart contracts are used to automate consent state changes, access token issuance, and workflow transitions. They do not have legal force by themselves; their relation to enforceable agreements depends on the surrounding governance.
On-chain: Data or logic that is stored and executed directly on the distributed ledger. On-chain storage is tamper evident but is visible to ledger participants and, on public chains, to anyone. Healthcare projects that put protected health information on-chain have generally found the design untenable on regulatory and privacy grounds.
Off-chain: Data stored outside the distributed ledger, typically in a conventional database or document store. Off-chain data can be linked to on-chain records through commitments such as hashes. Most credible biomedical blockchain designs keep clinical data off-chain and put only commitments, access logs, and consent state on-chain.
Hash: A fixed-length output produced by a cryptographic hash function applied to an input of arbitrary size. The same input always produces the same hash. A different input produces a different hash with very high probability. Hashes are used in biomedical blockchain designs to commit to a specific version of a record without putting the record itself on-chain.
Consent management: The systems and processes through which patients or research participants grant, scope, and revoke authorisation for data use. In a ledger-backed design, consent state is recorded on-chain as a verifiable artefact. The elements of a consent design include the authorisation, the scope, the revocation path, and the audit log.
Decentralised identifier: An identifier that can be created and resolved without depending on a single central registry. The resolution method is defined by a scheme-specific specification called a DID method. The specification for the identifier format and resolution protocol is maintained by a standards body. Decentralised identifiers are often used as the base layer for verifiable credential systems.
Verifiable credential: A digital statement about a subject, issued by a defined party, with a cryptographic signature that allows any relying party to check the signature and the issuer without contacting the issuer directly. In healthcare, verifiable credentials are used for provider licences, patient enrolment tokens, and consent receipts. The credential carries the claims; the chain carries the revocation state.
Interoperability: The ability of separate systems to exchange information and interpret it correctly without special configuration. In healthcare, interoperability requires agreement at multiple layers: vocabulary, identifier, message format, workflow, and policy. A ledger does not generate interoperability; it can carry the shared state that makes exchange tractable once the other agreements are in place.
Audit trail: A tamper-evident record of events, including who did what, to what, and when. Ledger-backed audit trails make retroactive alteration detectable and can be read by parties whose interests differ from the data custodian. In healthcare, audit trails support incident response, regulatory inspection, and patient transparency.
Data provenance: The documented origin, custody history, and transformation record of a dataset. In biomedical research, data provenance supports reproducibility, supports fraud detection, and satisfies the requirements of funders and publishers for data availability and integrity documentation. A ledger can carry provenance events in a form that is inspectable by external parties.
Genomic data marketplace: A platform through which individuals contribute genomic data in exchange for some form of return, typically tokens or research benefit, and through which researchers or companies purchase access to that data. Genomic data marketplaces raise specific consent, re-identification, and governance questions that distinguish them from ordinary health data sharing. The directory tracks projects in this category under the genomic data industry focus.
Clinical trial registry: A system for recording clinical trials before, during, and after execution. Registries exist to prevent selective reporting and to create a public record of planned research. Ledger-backed registry designs add tamper-evidence to protocol registration and amendment tracking. Pre-registration of analysis plans in this form supports claims that the analysis was specified before unblinding.
Patient-controlled record: A health record design in which the patient holds meaningful authority over who can access their records and for what purposes. Patient-controlled designs range from full self-custody, where the patient holds the access keys, to dashboard-mediated control, where the patient manages consent through an application while the records remain in institutional storage.
Zero-knowledge proof: A cryptographic protocol in which one party demonstrates knowledge of a fact to another party without revealing the fact itself. In healthcare applications, zero-knowledge proofs are used to assert properties of data, such as that a value is within a reference range, without revealing the underlying measurement. They reduce the minimum disclosure required to accomplish a given verification task.
Tokenomics: The design of the economic mechanics around a project's token: how tokens are issued, how they circulate, what they are redeemable for, and how their supply and demand dynamics are managed. In biomedical blockchain, tokenomics are most common in genomic marketplace and patient data marketplace designs. Credible tokenomics treat the token as a unit of utility rather than primarily a vehicle for speculation.
Permissioned network: A distributed ledger where participation, including the ability to read, write, or validate records, requires prior authorisation from a governing party or group. Permissioned networks can be made confidential within their participant set and are generally faster and more controllable than public networks. Healthcare blockchain projects most commonly use permissioned network designs.
Public network: A distributed ledger open to any participant who runs the required software, without prior authorisation. Public networks provide strong tamper evidence and independence of timestamp verification but offer no confidentiality: all transactions are visible to all participants. Most healthcare applications use public networks only for specific functions, such as certificate anchoring or analysis plan pre-registration, rather than for clinical data.
Private network: A distributed ledger whose participants are fully controlled by a single organisation or a tightly defined group. Private networks are operationally closer to a replicated database with cryptographic signing than to either a public or a consortium network. They may be useful inside a single enterprise but do not provide the trust properties relevant to multi-party healthcare exchange.