Directory Service

The ADEX Directory Service is a foundational component of the ADEX framework, enabling the secure discovery, registration, and coordination of surveillance data services across a distributed environment. Drawing conceptual inspiration from the Discovery and Synchronization Service (DSS) in InterUSS, the ADEX Directory facilitates a modular, federated ecosystem by acting as a trusted registry of available data feeds.

The directory service comprises a database and a set of APIs that are synchronised via the Hedera public ledger. Hedera acts as a distributed consensus layer across all directory instances, ensuring that service records are consistent, tamper-evident, and resilient to failure or manipulation via an aBFT consensus protocol.

The ledger provides cryptographic timestamping and auditability for every directory entry, making it possible to trace service availability, integrity changes, and operational history with full transparency. This enables directory providers to operate independently while remaining part of a coherent, synchronised ecosystem—eliminating the need for any single trusted intermediary and reinforcing the decentralised philosophy underpinning ADEX.

Function and Operation

At its core, the directory enables data providers (e.g. sensors, platforms and data servers) to publish metadata about the surveillance data they have available, while allowing clients (e.g. DAA systems, FIDs, UTM platforms) to query for and establish connections to those data services in real time.

• Registration: Each client or server can register metadata such as geographic coverage, update rate, latency, data format, and integrity confidence to one or more directory instances.

• Discovery: Clients query the directory using configurable filters (e.g. location, data quality, redundancy level) to identify relevant servers that meet operational or regulatory criteria.

• Connection: Once a suitable service is found, the client establishes a direct, authenticated point-to-point connection with the server, bypassing the directory entirely for runtime data flow.

Key Attributes

• Federated and Open: The directory is not a centralised platform. It is an open-source, interoperable specification that can be implemented and hosted by any compliant organisation, supporting jurisdictional flexibility and competitive innovation.

• Synchronised State: To ensure consistency across multiple directory instances, state synchronisation is achieved using the Hedera public ledger. This provides an immutable record of published services and enables secure coordination between independent operators.

• Resilience and Redundancy: Consumers can query multiple directory services in parallel, ensuring high availability and operational continuity. If one provider becomes unavailable or untrusted, alternate directories can be substituted without reconfiguration.

• Fine-Grained Filtering: The directory supports extensible metadata tagging, allowing consumers to identify feeds with specific capabilities (e.g. data type, location, quality, availability).

• Market Enabler: By decoupling discovery from delivery, the ADEX Directory creates a level playing field for both commercial and public sector participants. Specialised directories can offer differentiated services, from curated datasets to SLA-certified access, fostering innovation and service quality.

Strategic Value

The ADEX Directory Service is more than a technical registry, it is a governance and trust layer that enables scalable coordination without imposing centralised control. It ensures that operators, regulators, and service providers can interact within a common framework while maintaining autonomy, resilience, and auditability across the ecosystem.