NEXUS infrastructure · Registry
One public registry. Every certificate traceable.
Book-and-claim by design: each certificate is issued once, can change hands, and is retired only once, in the name of whoever makes the claim.Issued once, retired once, in the claimant's name.
02The certificate
Each certificate has a permanent identity.
A unique serial number and an HTTPS address that stays valid even after retirement.A serial number, a permanent address.
- Serial number and URI. Unique, and still valid after retirement.Unique, valid after retirement.
- What it certifies. Module, protocol and versions, project, basin, vintage.Module, protocol, project, basin.
- Who held it. The history of holders and the beneficiary of the retirement.Holders and beneficiary.
03Its life
Seven states, all tracked.
Every state of a certificate is recorded. Retired, split and cancelled are final.Every state recorded; three are final.
- Encumbered without being spent. Pledged as collateral for a financing; while the pledge runs, it can be neither retired nor transferred.Collateral, not spent.
- Retired, not revoked. Retirement consumes the certificate for one claim; only cancellation revokes it.Only cancellation revokes.
04No double counting
Spent once, like a bank balance.
The registry's code enforces the rule, not a reviewer's vigilance.Enforced by code.
- One quantity, one entry. Each verified quantity gives one registry entry.One quantity, one entry.
- Retired at most once. For one claim, by one party.One claim, one party.
- Executed by code. The rule runs in the registry, it is not left to review.Not left to review.
05Split
Split without ever duplicating.
When a sale does not match a lot's size, the lot turns inert and gives two child lots, each with its own address.Two child lots, never a copy.
- The parent lot turns inert. It can no longer move; its children carry the volume.The parent stops moving.
- Each child has its own URI. And can be split again, without limit.Its own address.
- The tree can be walked both ways. Anyone can trace a lot back to its original issuance.Back to the original issuance.
06Interoperability
Data that travels, without re-keying or losing its proof.
The registry speaks the formats of those who receive its data: corporate reporting, W3C verifiable credentials and the European water data spaces, under the FAIR principles. The registry remains the sole source of truth.Reporting, VC 2.0, European data spaces: one source of truth.
- Corporate reporting. Structured metadata, ready to reuse in your CSRD (ESRS E3), CDP Water or GRI 303 disclosures, without any claimed equivalence.Ready for CSRD, CDP, GRI.
- W3C Verifiable Credentials 2.0. Each certificate exports as a verifiable credential anyone can check without going through us, and links by its URI to the digital product passport.Checkable without us.
- European water data spaces. FAIR data built on SAREF4WATR, Smart Data Models, NGSI-LD, DCAT-AP and the IDSA Dataspace Protocol, the building blocks of the future water data space.FAIR, ready for the water data space.
07Get started
Want access to the registry?
Buyers, project developers, integrators: tell us your use and we open access.Tell us your use.
+Questions
What does book-and-claim mean?
The certificate is issued once, can change hands, and is retired by whoever makes the claim.
What is retirement?
The final step: the certificate is consumed for one claim, by one party.
Can a certificate be retired twice?
No. The rule is enforced in the registry's code: one quantity, one entry, one retirement.
Can the data be exported?
Yes: by API, as W3C VC 2.0 credentials, and in the formats of the European water data spaces (SAREF4WATR, NGSI-LD, DCAT-AP).
How do I get access?
Contact us: access is opened on request.