A new type of Google carousel seems to be imminent
While working on a code example for a schema.org/Product
listing page I noticed a warning message in Google's Structured Data Testing Tool, indicating I forgot to specify the schema.org/mainEntityOfPage
An interesting message as this is the first time, since the introduction of mainEntity/mainEntityOfPage, there's an indication Google has the intention of taking the presence of these properties into account.
Though what I find even more noteworthy is the reason why the SDTT gave this warning (emphasis mine):"A value for the mainEntityOfPage field is required.""Required by: List Page Carousels"
Now when you activate the link "what's this?"
you get directed to https://developers.google.com/structured-data/carousels/list-pages
- a page that currently still returns a 404.
So it looks like the SDTT accidently revealed something Google isn't ready to publicly announce yet. Something I think is wonderful as it seems that for the first time ever there webmasters will have a very clear reason to start marking up product listing pages.
I for one can't wait for the official announcement to find out what 'List Page Carousels will look like and what they will contain'.