The article and mediaContent items have a siteIds property which specifies a list of the sites the item is associated with. In a non-multisite environment, the siteIds property of these items should be null.
In a multisite environment, only items associated with the current site are returned by searches and repository queries. Note, however, that if an article or mediaContent item has a reference in its relatedArticles or relatedMedia property to a content item that is not associated with the current site, the referenced item is not filtered out automatically. So, for example, if a page displaying an article has a Related Media section with links to the items in the displayed article’s relatedMedia property, those links will render by default regardless of what sites the related items are associated with. However, you can use collection filters to restrict which links are rendered, based on the items siteIds properties. (Similarly, the startDate and endDate properties are ignored by default, but you can use collection filters to filter out items based on these properties.) See the Personalization Programming Guide for information about collection filters.
