Is it OK to have multiple items of the same Schema.org type on a page?

Question

I have a site which has three places where I would use Schema.org’s Organization (itemtype="http://schema.org/Organization"):

• the contact information with the affiliation for the contact person
• the site logo
• a profile for another organization

How will search engines tell these three apart? The first two point to the same organization, but in different contexts. The last one does not represent our site at all but is a detailed profile for another organization. Will search engines know which ones refer to us and which one doesn't?

Answer 1

If it’s the same entity (on the same document) you describe, then don’t use multiple items. You should only use one item in this case. If your markup makes it hard to nest all properties under this item, use the itemref attribute (see example).

If these are different entities, use multiple/different items: one item per entity.

So in your specific example, you should use one item for your organization, and one item for the other organization’s profile.

To make clear that items are about the same entity, Microdata provides the itemid attribute. However, Microdata requires that vocabularies have to explicitly support "global identifiers for items", which is currently not the case for Schema.org. If itemid is supported, you could even have several items about the same entity on the same page. Until that is possible, and also in addition, you could use other properties that could serve as hint that items are about the same thing, for example url.