How to use additionalType and sameAs to link to Wikipedia

Linking to authoritative knowledge bases (like Wikipedia and Wikidata) is a great way to leverage rich content in your structured data. We usually recommend using additionalType or sameAs, but there are key differences in the way these properties work. Read on to learn how to use them to your advantage.

TABLE OF CONTENTS

• What is additionalType?
• When should I use additionalType?
• What is sameAs?
• When should I use sameAs?

What is additionalType?

While Schema.org has hundreds of types to choose from, sometimes you can't find one that's specific enough for the content you're marking up. The additionalType property allows you to reference external vocabularies with narrower terms to suit your needs.

When should I use additionalType?

Think of this property as providing a more specific term for the type you're connecting it to. For example, Schema.org doesn't have a specific type for bridal shop. Instead, we would mark it up as an instance of LocalBusiness and state it has the additionalType https://www.wikidata.org/entity/Q56064815 (Bridal shop).

Note that additionalType should only be used for entities that could be considered a narrower type of the Schema.org term you're linking it to. For example, the bridal shop Local Business would not have the additionalType https://www.wikidata.org/entity/Q353673 (Bride) because, a Bride is a type of Person, not a retail location.

What is sameAs?

Often times you'll be creating markup for a website (or entity) that's already described elsewhere. The sameAs property was created to state that an entity is exactly the same as an entity from another source. Using the sameAs property means the entity you're markup up inherits all of the same information, attributes and relationships of the external source.

When should I use sameAs?

The sameAs property is often used in the following scenarios:

• An Organization, Brand or Person also exists on Wikipedia or Wikidata
• An Organization, Brand has social media sites (Instagram, Twitter, Youtube, etc.).
• A location or place exists on Wikipedia or Wikidata

For example, Schema App (schemaapp.com) is the sameAs https://twitter.com/schemaapptool and https://www.linkedin.com/company/2480720/

Can I use Google Knowledge Graph Machine IDs as a sameAs URL?

Absolutely. Google uses Machine IDs to unique identify entities in their knowledge graph. These are often represented in the following format: /m/0dnf6m. You can turn this into a valid URL by adding kg: in front of the machine ID, making the full URL kg:/m/0dnf6m.