Introduction to JSON-LD#

JSON-LD (JavaScript Object Notation for Linked Data) is a lightweight data interchange format designed to integrate linked data principles with the simplicity of JSON. It is widely used to describe and share structured data on the web in a machine-readable format, making it ideal for semantic web applications.

Why JSON-LD?#

JSON-LD provides a way to:

  • Link data across different systems and domains using globally unique identifiers (IRIs).

  • Maintain compatibility with standard JSON, making it accessible to developers already familiar with JSON.

  • Enhance data interoperability and reusability by embedding semantics directly in the data.

  • Enable easy integration with linked data tools and ontologies like EMMO.

Key Features#

  1. Context: The @context keyword defines the mapping between JSON terms and their corresponding IRIs, allowing data to be unambiguously understood across different systems.

    Example: ```json {

    “@context”: {

    “name”: “http://schema.org/name”, “age”: “http://schema.org/age”

    }, “name”: “Alice”, “age”: 30

  2. Identifiers: JSON-LD uses the @id keyword to define unique identifiers for objects, enabling linking between entities.

    Example: ```json {

    “@id”: “http://example.org/person/alice”, “name”: “Alice”

  3. Types: The @type keyword specifies the type of an object, often linked to an ontology class.

    Example: ```json {

    “@type”: “http://schema.org/Person”, “name”: “Alice”

  4. Relationships: JSON-LD uses properties to define relationships between entities.

    Example: ```json {

    “@context”: {

    “friend”: “http://schema.org/knows”, “Person”: “http://schema.org/Person”

    }, “@type”: “Person”, “name”: “Alice”, “friend”: {

    “@type”: “Person”, “name”: “Bob”

    }

Getting Started with JSON-LD#

  1. Define a Context: The context maps your terms to IRIs. Use existing vocabularies like Schema.org or create your own.

  2. Model Your Data: Identify the entities, properties, and relationships in your domain.

  3. Use Ontologies: Integrate ontologies like EMMO to provide semantic meaning to your data.

  4. Validate Your Data: Use tools like the [JSON-LD Playground](https://json-ld.org/playground/) to test and validate your JSON-LD.

Advantages of JSON-LD#

  • Human-Readable and Developer-Friendly: JSON-LD retains the simplicity of JSON while embedding powerful linked data capabilities.

  • Extensible: JSON-LD can be easily extended with new terms and vocabularies.

  • Integration with the Web: JSON-LD is supported by major search engines and tools for rich semantic annotations.

Example: Electrochemical Cell in JSON-LD#

```json {

“@context”: {

“@vocab”: “https://w3id.org/emmo/domain/electrochemistry#”, “hasNegativeElectrode”: “https://w3id.org/emmo/domain/electrochemistry#hasNegativeElectrode”, “hasPositiveElectrode”: “https://w3id.org/emmo/domain/electrochemistry#hasPositiveElectrode”, “hasElectrolyte”: “https://w3id.org/emmo/domain/electrochemistry#hasElectrolyte”

}, “@type”: “ElectrochemicalCell”, “hasNegativeElectrode”: {

“@type”: “ZincElectrode”

}, “hasPositiveElectrode”: {

“@type”: “ManganeseDioxideElectrode”

}, “hasElectrolyte”: {

“@type”: “AlkalineElectrolyte”

}

}#

Example: A Simple Description of a Person

Below is an example of JSON-LD code for describing a person:

{
    "@context": "https://schema.org",
    "@type": "Person",
    "name": "Marie Curie",
    "birthDate": "1867-11-07",
    "spouse": {
        "@type": "Person",
        "name": "Pierre Curie"
    }
}

Learn More#

To dive deeper into JSON-LD, explore the following resources: