Public Attestation

This feature should be considered Alpha.

RFC

VCDM Verifiable credentials are a way to prove an attestation. Valid credentials prove statements of the form Issuer claims X, where X is itself a statement. One property of verifiable credentials is that the holder may keep them private simply by not sharing them with other parties. That property will be sometimes useful, sometimes not. VCDM crededentials are private and therefore not automatically discoverable but Public Attestations give a decentralized identity the ability to post claims that are discoverable by any party. For Dock DIDs, attestations are linked on-chain but Public Attestations are not specicfic to Dock. Other DID methods can implement public attestations by including them in DID documents.

Public Attestations are posted as RDF documents. Since RDF can represent, or link to, arbitrary types of data, Public Attestations can be used to publish arbitrary content.

Data Model

Public Attestaions live in the DID document of their poster. A DID with a public attestation will have an extra property, "https://rdf.dock.io/alpha/2021#attestsDocumentContent". The value of that property is an IRI that is expected to point to an RDF document. Any statement contained in that document is considered to be a claim made by the DID.

If DID attestsDocumentContent DOC then for every statement X in DOC DID claims X.

Two IRI schemes are supported for pionting to attested documents: DIDs and ipfs links. DIDs are dereferenced and interpreted as json-ld. Ipfs links are dereferenced and interpreted as turtle documents. The sdk makes it easy to dereferece DIDs and ipfs attestation documents but the Public Attestation concept is extendable to other types of IRI, like hashlinks or data URIs.

For Dock DIDs public attestation are made by setting the attestation for the DID on-chain. Changing the value of an attestation effectively revokes the previous attestation and issues a new one. A DIDs attestation can also be set to None, which is equivalent to attesting an empty claimgraph. Dock DIDs have their attestation set to None by default. A Dock DID with attestation set to None will not contain the attestsDocumentContents key.

Example of A DID attesting to a document in ipfs

did:ex:ex:

{
  "@context": "https://www.w3.org/ns/did/v1",
  "id": "did:ex:ex",
  "https://rdf.dock.io/alpha/2021#attestsDocumentContent": {
    "@id": "ipfs://Qmeg1Hqu2Dxf35TxDg19b7StQTMwjCqhWigm8ANgm8wA3p"
  }
}

Content of ipfs://Qmeg1Hqu2Dxf35TxDg19b7StQTMwjCqhWigm8ANgm8wA3p:

<https://www.wikidata.org/wiki/Q25769>
  <https://www.wikidata.org/wiki/Property:P171>
  <https://www.wikidata.org/wiki/Q648422> .

From these documents we can derive two facts. The first fact is encodeded directly in the DID document.

Fact 1:

# `did:ex:ed` attests to the content of `ipfs://Qmeg1..`
`<did:ex:ed> <https://rdf.dock.io/alpha/2021#attestsDocumentContent> <ipfs://Qmeg1..> .

The second fact is infered. Since we know the content of ipfs://Qmeg1.. we know that ipfs://Qmeg1.. contains the statement wd:Q25769 wd:Property:P171 wd:Q648422 (Short-eared Owl is in the genus "Asio"). did:ex:ex attests the document ipfs://Qmeg1.. and ipfs://Qmeg1.. states that the Short-eared Owl is in the genus "Asio", therefore:

Fact 2:

@prefix wd: <https://www.wikidata.org/wiki/> .
# `did:ex:ex` claims that the Short-eared Owl is in the genus "Asio".
<wd:Q25769> <wd:Property:P171> <wd:Q648422> <did:ex:ex> .

Example of A DID attesting to multiple documents

While it is valid DIDs to include multiple attested IRIs in a single DID document, Dock artificially limits the number of attestation to one per Dock DID. This is to encourage off-chain (ipfs) data storage. If a DID wishes to attests to multiple documents, there are two suggested options: 1) merge the two documents into a single document or 2) attest to a single document which in turn notes an attestsDocumentContents for each of it's children. The following is an example of option "2)".

did:ex:ex:

{
  "@context": "https://www.w3.org/ns/did/v1",
  "id": "did:ex:ex",
  "https://rdf.dock.io/alpha/2021#attestsDocumentContent": {
    "@id": "ipfs://Qmeg1Hqu2Dxf35TxDg19b7StQTMwjCqhWigm8ANgm8wA3p"
  }
}

ipfs://Qmeg1Hqu2Dxf35TxDg19b7StQTMwjCqhWigm8ANgm8wA3p:

<did:ex:ex>
  <https://rdf.dock.io/alpha/2021#attestsDocumentContent>
  <ipfs://QmXoypizjW3WknFiJnLLwHCnL72vedxjQkDDP1mXWo6uco> . # document1
<did:ex:ex>
  <https://rdf.dock.io/alpha/2021#attestsDocumentContent>
  <ipfs://QmdycyxM3r882pHx3M63Xd8NUfsXoEmBnU8W6PgL9eY9cN> . # document2

Uses

Two properties of RDF have the potential to supercharge Public Attestations.

  1. It's a semantic knowlege representation, it can be reasoned over.
  2. It's queryable in it's native form.

Via these properties the sdk implements a "Curious Agent". The Curious Agent seeks out information. It starts with an initial kernel of knowlege (an RDF dataset) and it follows a sense of curiosity, gradually building it's knowlege graph by dereferencing IRIs, stopping when it finds nothing new to be curious about. As it crawls, it reasons over the information it's found, deducing new facts, which may in turn spark new curiosity. The Curious Agent accepts it's curiosity as Sparql queries. The logical rules it uses to reason are also configurable, axioms are provided to the Agent as conjunctive if-then statements (like in Claim Deduction). Within the sdk, the Curious Agent is simply called crawl().

The Curious Agent is sometimes referred to as "the crawler".

The use-case that drove implementation of the crawler is to search for publicaly posted Delegation information. As such, a bare minimum of functionality is implemented by crawl(). Want more? Consider contacting us.