Why does 'category' expect PhysicalActivityCategory?

The 'category' property [1] expects one of these types:

- PhysicalActivityCategory
- Text
- Thing

Why is it that it explicitly lists PhysicalActivityCategory in addition 
to Thing?

In the docs [2] it says:

 > In addition, whenever an expected type is specified, it is also fine
 > to embed an item that is a child type of the expected type.

As PhysicalActivityCategory is a child type of Thing, wouldn’t it be 
sufficient to list Thing?


Stefan


[1] http://schema.org/category
[2] http://schema.org/docs/gs.html#schemaorg_expected

Received on Friday, 11 April 2014 12:18:51 UTC