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RFC-74 : Semantic Linking

Champion: @andrea-gioia

Summary

A semantic link is an explicit connection between a data asset exposed by a data product through one of its output ports and one or more concepts defined in a central enterprise ontology.

Motivation

Semantic linking is a way to bring semantics to a data product and improve its capability to be discovered, reused, and composed with other data products belonging to different domains.

Design and examples

{
    "$schema": "http://json-schema.org/draft-07/schema#",
    "title": "Simplified Movie Object (Compact)",
    "type": "object",

    "s-context": {
        "s-base": "https://schema.org",
        
        "s-type": "[Movie]",

        "movieId": null,
        "directorName": "director[Person].name",
        "directorCountryName": "director[Person].country[Country].name",
        "actors": "actor[Person].name",
        "copyright": {
            "s-type": "copyrightHolder[Organization]",
            "organizationId": null,
            "email": "contactPoint[ContactPoint].mail"
        }  
    },

  
    "properties": {
      "movieId": {
        "type": "string"
      },
      "name": {
        "type": "string"
      },
      "directorName": {
        "type": "string"
      },
      "directorCountryName": {
        "type": "string"
      },
      "actors": {
        "type": "array",
        "items": {
          "type": "string"
        },
        "minItems": 1
      },
      "copyright": {  
        "type": "object",
        "properties": {
            "organizationId": {
                "type": "string"
            },
            "legalName": {
                "type": "string"
            },
            "email": {
                "type": "string"
            }
        }
      }
    }
  }

Explanation:

  • s-context: defines the semantic links. It can be defined inline or as an external reference
  • s-base: the base URL used to resolve concept names
  • s-type: the linked concept name or full concept URI enclosed in square brackets. The name before the brackets is the name of the parent property valorized by the linked concept. For example "copyright": {"s-type": "copyrightHolder[Organization]"} maps the property copyright of the schema to the property copyrightHolder of the parent concept (Movie) and has as value an Organization concept. If the name used in the schema is already equal to the name of the referenced concept property it can be omitted in the mapping.
  • "movieId": null, the schema property movieId is not defined in the Movie concept. It exists only in the physical data
  • "directorName": "director[Person].name" : the property directorName in the schema is linked to the property name of the Person who directs the Movie
  • "directorCountryName": "director[Person].country[Country].name" : the property directorCountryName in the schema is linked to the property name of the Country of the Person who directs the Movie
  • actors": "actor[Person].name : the property actors in the schema is linked to the property name of the Person who acts in the Movie. Because actors in the schema is an array the values are the names of the actors.

Alternatives

The alternative to use REST API Linked Data Keywords has been rejected because is not possible to manage easily semantic linking in flat schemas

Decision

  • Define semantic links using a custom sub-specification
  • Define semantic links as a particular type schema annotations

Consequences

  • We need to create a new specification
  • We need to work on this RFC together with the RFC related to schema annotation

References