Use less specific type from core or more specific type from extension?

Question

I'd like to mark up a bit of a web page displaying info about a PhD thesis. I see in the Schema.org vocabulary, after clicking "Core plus all extension vocabularies", that there's a type Thesis defined in the Bibliographic Extension (bib).

I now face a choice between using Thesis from the extension, or something less accurate from the core, e.g. CreativeWork, or maybe (slightly incorrectly), ScholarlyArticle.

My main goal is to make mainstream search engines understand my content. In particular, my goal is NOT to be discoverable by some specialized academic SE that perhaps has extra support for such an extension.

Can I use Thesis or will that mean nothing to Google and other general-purpose SEs?

Answer 1

Hosted extensions are reviewed and part of the Schema.org vocabulary; they use the same namespace as Core.

Every consumer should handle them fine (but, of course, you can never know for sure, and you can never know all of them). Consumers that are only interested in specific data will recognize only a certain set of types/properties, but there is no reason to assume that this set will exclusively consist of Core terms.

If you are unsure that a type is recognized by a consumer (e.g., because the type is new, because it’s in a hosted extension, because the consumer is rarely updated etc.), you can specify suitable types in addition:

<!-- Microdata -->
<div itemscope itemtype="http://schema.org/Thesis http://schema.org/CreativeWork"></div>

<!-- RDFa -->
<div typeof="schema:Thesis schema:CreativeWork"></div>

<!-- JSON-LD -->
<script type="application/ld+json">
{
  "@context": "http://schema.org",
  "@type": ["Thesis", "CreativeWork"]
}
</script>

(For a consumer that recognizes Thesis, this is not needed, because CreativeWork is defined to be a parent type.)