Yes, if you want to relate the items to the WebPage, you have to use a property.
For the main content, we have mainContentOfPage
. But what about elements that are not (part of) the main content?
Here’s a discussion about such a generic property for linking a WebPageElement to WebPage:
Am I right that WebPage lacks a generic property for linking to WebPageElement?
There is a proposal for a hasPart
property: "A related CreativeWork that is included either logically or physically in this CreativeWork". This would be a good match, but until it becomes part of Schema.org (if at all), we’d have to use what is already there.
Possible existing properties could be:
text
has the problem that it expects Text, not another item. citation
is probably, at least according to its description, meant for more specific cases. That leaves us with mentions
and about
, but both aren’t really fitting either.
So I’d say: Currently there is no good solution.
Personally, I’d just omit a property and leave the item unlinked (until a suitable property gets added to Schema.org).