Such files do not contain explicit specification attributes, but they are referenced from primary specification files located nearby.

The following example contains two files located in the same directory. First one is a plain primary specification file. Second is referenced from the first one and thus is suggested to be considered a specification too.

Primary specification file openapi.yaml:

openapi: 3.1.0
components:
  schemas:
    CustomSchema:
      description: Custom schema object
      properties:
        foo:
          $ref: 'common.components.yaml#/components/schemas/CommonSchema'

Specification file candidate common.components.yaml:

components: # 'Mark file as OpenAPI specification' highlighting
  schemas:
    CommonSchema:
      description: Common schema object reused in several specifications