Categories for Product in schema.org?
Using as a reference: https://support.google.com/webmasters/answer/146750?hl=en
You will notice under 'Product' that there is a category Property, and furthermore there's an example on down the page:
<span itemprop="category" content="Hardware > Tools > Anvils">Anvils</span>
which I've mimic'd exactly:
<span itemprop="category" content="kitchen sinks > stainless steel sinks > undermount">undermount</span>
Yet when I test it with Google's structured data tool, I get the error:
Error: Page contains property "category" which is not part of the schema.
I realized in the example also, it's using data-vocabulary.org→Product, where I'm using schema.org→Product.
Now on http://schema.org/Product, it does not have category anywhere mentioned. Does schema.org not offer categories? Or am I missing something?
Answer
category is an itemprop of schema/Offer, not schema/Product
To fix your problem, place an offer within the product, and attach the category to the offer.