Google Structured Data Testing Tool - improved support for multiple independent types

A quick note to let folk here know of recent improvements to Google's
Structured Data Testing Too
<https://search.google.com/structured-data/testing-tool>l. Some of you have
been asking for this ... for a while.  The tool now allows multiple
independent types to be applied to a single entity without errors/warnings.

For example, Book and Product are defined as independent branches of the
schema.org type hierarchy. And yet it is sometimes appealing to combine
"book-ish" and "product-ish" properties on a single item / entity, i.e.
sometimes a thing can be both at once.

e.g. like this,

{
  "@context": "http://schema.org/",
  "@type": ["Product", "Book"],
  "name": "books can be products!",
  "gtin13": "1234",
  "isbn": "5678"
}

Previously this kind of structure made the Google testing tool complain
needlessly. The final part of the fix for this recently went live, so you
should now see a more sensible response
<https://search.google.com/structured-data/testing-tool?url=https://gist.githubusercontent.com/danbri/10bcf62cba95a0a20a30ee8a78246774/raw/45e0dde4b681963e442be44cfd1d725e7726f6c9/gistfile1.txt#url=https%3A%2F%2Fgist.githubusercontent.com%2Fdanbri%2F10bcf62cba95a0a20a30ee8a78246774%2Fraw%2F45e0dde4b681963e442be44cfd1d725e7726f6c9%2Fgistfile1.txt>
to this sort of markup, which now includes a simple "/"-separated list of
the types that were found. And less complaining.

Here's a Microdata example,

<div itemscope itemtype="https://schema.org/Book https://schema.org/Product
">
   <span itemprop="name">books can be products!</span>
   <span itemprop="gtin13">1234</span>
   <span itemprop="isbn">5678</span>
  </div>

And RDFa 1.1,

<div vocab="https://schema.org" typeof="Product Book">
   <span property="name">books can be products!</span>
   <span property="gtin13">1234</span>
   <span property="isbn">5678</span>
</div>

As schema.org's vocabulary has grown, the possibility to mix together
pieces of complementary vocabulary like this is increasingly useful. I hope
the conformance section of the schema.org site - see
http://schema.org/docs/datamodel.html - makes clear that this flavour of
schema.org description is very much in the spirit of the project...

cheers,

Dan

ps. only loosely related, but I was recently asked about combining RDFa and
Microdata within the same section of markup. It can be done, although
probably always a bad idea:
https://twitter.com/danbri/status/827492508426964994

pps. this notion of multiple-types shouldn't be confused with a related
situation, which is where schema.org itself says that *all* members of some
type are always members of multiple supertypes. We don't do this often, but
for example we say that anything which is a LocalBusiness is going to also
be both an Organization and a Place. The approach I'm talking about today
is about allowing anyone to mix together types when it seems sensible /
appropriate, without the combination being explicitly anticipated by the
schema.org project.