I agree with you that "identity" is not well defined in Apple's document. The way I'm reading it is that "identity" is anything that uniquely identifies each u

I agree with you that "identity" is not well defined in Apple's document. The way I'm reading it is that "identity" is anything that uniquely identifies each user of your app, i.e. something like a GUID or any generated user ID. It does not necessarily mean that you are able to identify the real-world person behind the user record. So for instance, if you collect the number of steps each user has taken each day and you store that information on your server associated with a user ID, then you have collected that data and you have linked it to the user's identity, even if you know absolutely nothing else about that user. What would it mean to collect data without linking it to a user's identity? I think it means collecting aggregate or statistical data. If you transmit the number of steps taken by each user to your server, but you only ever store the average number of steps taken across all your users, then you have collected data without linking it to a user's identity. For email addresses the distinction between collection and linking to users makes no sense. It's always going to be both or neither. So that's what I believe. What's important though is what Apple actually means. And I fully agree with you that this document needs clarification.