问题
On a product page I have two aggregated ratings for one product at different places, which means they contain identical information. I want to have them twice on that page due to ux reasons, but I'm not sure if I can markup them with schema.org everytime or if this would be a useless duplication.
Wondered if there is a solution with itemref but in my opinion it's not helpful for this task.
回答1:
Unless you use itemid, consumers can’t be sure that two (or more) items are (about) the same thing. So they would learn that your Product item has two AggregateRating items. Consumers might try to deduce that both items should be the same (e.g., by comparing url values), but you would better not rely on this.
So you should use the itemid attribute (Schema.org does not yet claim to support it, which Microdata requires, but according to this issue, it’s intended to document it sometime), giving both of your AggregateRating items the same URI.
But consumers don’t necessarily support itemid, so they might still have problems guessing that these items are about the same thing.
So ideally: markup only one occurence (per document) with Schema.org.
来源：https://stackoverflow.com/questions/28625426/is-it-okay-to-use-same-schema-org-markup-twice-on-one-page