ID number or URI title as identifier for content postings Sites or apps that use URI/URL as the unique identifier for content pages example http://somesite.com/this-is-a-test-post * Ghost blog app Sites or apps that use an all-numeric ID number as the identifier along with or maybe not the friendly URL of the title example http://somesite.com/12345 or http://somesite.com/12345/this-is-a-test-post * qz.com