Specify a mechanism for schema.org props to be defined on new types

[nickevansuk]

Currently there is no way to know from the model files whether a defined schema.org property on a schema.org type is actually associated with the type in schema.org, or whether it's a new association within the OpenActive model (i.e. the OpenActive model associates an existing schema.org property with an existing schema.org type, where that association does not exist in schema.org).

This will help ensure that implementations that inherit from schema.org models can do so correctly.

[henryaddison]

Hi @nickevansuk, based on the call yesterday just checking for some guidance, perhaps an example model affected by this, as to the output desired for this (is it some extra key in such fields of the JSON model specification files and a test that confirms fields do or don't exist already as properties on any derived schema.org type?).