Json ld

JSON-LD stands for JavaScript Object Notation for Linked Data. It’s a type of JSON format that is used to encode linked data using a set of standards based on the W3C's RDF (Resource Description Framework).

Here’s an example of a JSON-LD file:

{
  "@context": "https://schema.org",
  "@type": "Person",
  "name": "Jane Doe",
  "jobTitle": "Developer",
  "telephone": "(425) 123-4567",
  "url": "<http://www.janedoe.com>"
}

In JSON-LD, a vocabulary is a set of terms that define the meaning of JSON-LD data. The vocabulary is defined in a JSON-LD context, which is a JSON object that maps terms to their corresponding IRIs (Internationalized Resource Identifiers).

The @context element

A vocabulary is a URL where you can find schemas for structured data to be used online. Each vocabulary source (https://schema.org/, for example) defines entities, relationships between entities and actions. The @context element defines the vocabulary used in the file, making it more human-readable, easier to understand and helping the browser understand the context of the data and its relationships.

By providing a link to the vocabulary, the @context element clarifies what the data represents and ensures that it’s interpreted properly. This makes easier the translation between schemata or systems and the reconstruction of lost or foreign contexts in the case these are lost.

In the previous example, the @context says “Hey browser, the vocabulary I’m referencing is http://schema.org".

The @type element

This element specifies the type of the item being marked up. You can find a list of all the available item types here.

In the previous example, the @type says “Hey browser, the item type I’m using is Person". You can find it here.

Attribute-value pairs

After defining the vocabulary and the item type, you can define the item properties. Inside an item type's Schema.org page (for example http://schema.org/Person), you will find all available properties that an item Person can have. In the previous example, name, jobTitle, telephone and url are all its properties.

JSON-LD and Verifiable Credentials

JSON-LD is a format that allows for easy integration of Verifiable Credentials into existing systems, and it provides a standardized way of representing identity-related information. JSON-LD is the perfect format to help ensure VCs interoperability, usability and easy manageablity.

Here's an example of a verifiable credential in JSON-LD format:

{
  "@context": [
    "https://www.w3.org/2018/credentials/v1"
  ],
  "type": ["VerifiableCredential", "UniversityDegreeCredential"],
  "issuer": "https://example.edu/issuers/14",
  "issuanceDate": "2021-06-01T17:00:00Z",
  "credentialSubject": {
    "id": "did:example:ebfeb1f712ebc6f1c276e12ec21",
    "degree": {
      "type": "BachelorDegree",
      "name": "Bachelor of Science and Arts",
      "degreeType": "BachelorDegree",
      "college": "College of Engineering and Applied Science",
      "university": "Example University"
    }
  },
  "proof": {
    "type": "Ed25519Signature2018",
    "created": "2021-06-01T17:00:00Z",
    "proofPurpose": "assertionMethod",
    "verificationMethod": "did:example:ebfeb1f712ebc6f1c276e12ec21#keys-1",
    "jws": "eyJhbGciOiJFZERTQSIsInR5cCI6IkpXVCJ9.eyJzdWIiOiJkaWQ6ZXhhbXBsZTpiMzllZjJhZjM1NzY2ZGE2M2Q5MmUxMzAwMjQyMmVjMzIyNjVhYTE3IiwiaXNzdWVyIjoiaHR0cHM6Ly9leGFtcGxlLmVkdS9pc3N1ZXJzLzE0IiwiaWF0IjoxNjIyMjAzMTM4LCJleHAiOjE2MjIyMDMxNzgsImp3ayI6eyJrdHkiOiJFQyIsImNydiI6IlAtMjU2In19..5uMz5N5R5C5vK1V7Bp5G9fWbq3qkijxHx6GpUudKdJqAywq6HnGX6kGPEA9KjZlYi4f4sH4b4C8QsFyj-oCg"
  }
}

This Verifiable Credential is a University Degree Credential, issued by Example University to a specific individual identified by a DID. The credential contains information about the degree earned, including the degree type, name, college and university. The credential also includes a proof that it was issued by Example University and that the information it contains has not been tampered with.