Re: [HDP] Agentic delegation provenance with DID principal binding

Hi Bob,



Thank you for the detailed and thoughtful feedback, this is exactly the high-quality review I was hoping for.



On the scope object and ODRL: I appreciate the clear mapping and the interoperability/VC benefits (especially via termsOfUse). However, my intent is to keep HDP strictly as a provenance and audit-trail record. The scope is a lightweight signed description of intended delegation for the evidence trail, while enforcement, violation detection, and policy reasoning remain application-layer concerns, handled by enterprise agentic threat detection software such as Helixar 360 (the commercial platform I created) and similar tools.



Adopting a full ODRL Policy would shift HDP toward general policy carriage, moving away from its narrow chain-focused provenance goal. I'll strengthen the related work section in v0.2 to better cover ODRL and the trade-offs of vocabulary reuse vs. minimal token format.



Your broader idea of a payload-agnostic chain-of-custody core with profiles (agentic delegation, data provenance, consent, etc.) is compelling and the novelty really is in the tamper-evident append-only chained structure. Worth exploring longer-term, though likely too large for v0.2.



I'd value your thoughts on keeping the scope minimal for provenance while improving VC alignment.



Thanks again, feedback like this is incredibly valuable.



Best regards, 

Siri Dalugoda 

Helixar






---- On Tue, 31 Mar 2026 10:36:55 +1300 Bob Wyman <bob@wyman.us> wrote ----



Siri,
Thank you for sharing HDP. The delegation chain model is very interesting and useful. I've been working with similar issues and offer these observations:

The W3C ODRL gap
HDP's scope object reinvents vocabulary that ODRL (W3C Recommendation) already provides:
 authorized_tools → ODRL action with asset targets

 authorized_resources → ODRL target

 constraints (action_count, time_window) → ODRL constraint with existing operators

 persistence / network_egress → ODRL prohibition


The cost of not inheriting from ODRL is concrete:
First, vocabulary fragmentation. Systems that already understand ODRL (there are several, particularly in the rights management and VC ecosystem) cannot reason about HDP scopes without a separate parser and separate policy reasoning tooling. This duplicates functionality unnecessarily.

Second, lost composability. ODRL policies compose: you can express "this agent may read financial documents unless classification is restricted, and must log every access" in a single policy that standard engines evaluate consistently. HDP's constraint array is a bespoke constraint language that replicates this without the composability.

Third, the VC alignment. You note that you see "a natural alignment between HDP's delegation model and the VC data model" and want to formalise it in the next revision. The VC Data Model 2.0 already has a termsOfUse property (section 5.5) for expressing policies attached to a credential, and ODRL is an established vocabulary for populating it. If HDP's scope were an ODRL Policy, the VC binding would follow naturally from existing practice rather than requiring new formalisation.


Recommended v0.2 change
Replace the novel scope object with an ODRL Policy document. HDP-specific fields with no ODRL equivalent — intent, poh_credential, max_hops — become ODRL extensions under the x- namespace HDP already defines for extensibility. This preserves all HDP semantics while gaining ODRL interoperability, composability, and the VC binding the CG audience would expect without requiring additional formalisation.

A broader architectural observation
Asking what remains of HDP if scope becomes an ODRL Policy document leads somewhere interesting. What if "scope" could be any payload?

What remains of HDP if scope becomes generic: header (standard token envelope), principal (the human anchor with DID binding and optional proof-of-human credential), and chain[] (the hop-by-hop append-only record with cumulative hash chaining). The genuine novelty in HDP lies in its chain structure: each hop extends a signed record over all prior states, gaps in sequence numbers indicate tampering evidence, and any party can verify the entire chain offline without a registry.

Notice that the chain structure says nothing about authorisation specifically. The scope field is a payload. There is no structural reason that payload has to be an authorisation policy. It could equally carry:
Data provenance: This dataset was derived from these sources, passed through these transformations, and met these conditions

Consent delegation: This patient authorised this use of their data, delegated to this researcher, and then to this analysis tool

Content moderation: A human reviewed this content, which was then passed to this classifier and flagged by this tool

Financial instruction: This officer authorised this transaction, delegated it to this system, and this agent executed it.

Physical-world command (as your HDP-P paper already explores): This action was authorised by this operator, delegated to this robot, executed by this actuator


In every case the invariant is identical: a human principal initiates a chain, each hop extends it with a signed record, any party can verify the full chain offline, gaps are detectable. The chain mechanism is the protocol. The payload is a profile.

This suggests HDP could be specified at two levels: a payload-agnostic generic chain-of-custody protocol defining the chain structure, signing rules, and verification procedure; and a set of named profiles, of which ODRL-scoped agentic delegation is the first, data provenance is an obvious second, and consent management is a third, etc.

That separation would make HDP a broadly applicable provenance infrastructure rather than a single-purpose agentic authorisation token. The IETF draft would be the generic protocol; the profiles would be separate documents. The core enabling structure, the chain structure, would clearly separate from the application-specific vocabulary.

This is a larger architectural suggestion than the ODRL point, and may be more than you want to take on in v0.2. But it seems worth raising while the design is still open, because retrofitting payload-agnosticism into a protocol after it has been specified around a fixed payload type is hard.

Thanks again for an interesting spec!

bob wyman




On Mon, Mar 30, 2026 at 3:59 PM Siri Dalugoda < mailto:siri@helixar..ai > wrote:





Hi Credentials CG Team,



I'd like to share a protocol that addresses a gap in the agentic AI space that I believe is directly relevant to this group's work on Verifiable Credentials and decentralized identity.



HDP (Human Delegation Provenance Protocol) defines a signed token chain that creates a cryptographic audit trail from an authorising human to every AI agent acting downstream. 

The principal identity model supports id_type: "did" natively, meaning a W3C DID can be used as the root authorising identity binding HDP delegation chains to existing decentralised identity infrastructure.



IETF draft: https://datatracker.ietf.org/doc/draft-helixar-hdp-agentic-delegation/ 

Spec:       https://helixar.ai/about/labs/hdp/ 

Repository: https://github.com/Helixar-AI/HDP 



Key properties:

- Ed25519 signatures over RFC 8785 canonical JSON

- Fully offline verification, no registry or network dependency

- DID-compatible principal binding at the root token level

- Compact enough for HTTP header transport (X-HDP-Token)



I see a natural alignment between HDP's delegation model and the VC data model, specifically around how an AI agent's authority could be expressed as a Verifiable Presentation derived from the root delegation token.

I'm actively exploring this in the next draft revision and would welcome input from this group on how best to formalise that binding.



Happy to answer questions or take feedback on the draft.



Best regards,

Siri

Helixar Limited