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?
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.
I've been working on JSON-ld & microdata a lot recently, and I believe in your case 'category' needs to be placed in a meta tag, not span/div tag, preferably before your item. Logically, your need to identify 'undermount' is redundant as it would already be included within your content. Oddly, the schema type service has 'serviceType' as a property, but product does not have an equivalent, otherwise that could have been another workaround. For your content 'undermount' use itemprop="name" within your span, no content within that tag necessary.
Note: You are using a
content
attribute onspan
, which is not valid in HTML5 or Microdata (but in RDFa).Schema.org has a
category
property, but it can not be used onProduct
. Depending on your content, you may want to useOffer
instead of Product (see also my answer with an example use ofcategory
).Here is the correct format accepted by schema.org...