Reconciliation of users

On W3C Personalization Tools 1.0, section 2.2 Reminders and Messages, you go:

For example, users can disable push notifications and messages on applications such as Skype and Facebook across different devices, however, they may forget to re-enable these notifications and messages. The following defined values allow an alternative solution for users to manage reminders and messages by forming a cross-application and cross-device matrix that manages all reminders and messages. These values are based on a matrix for reminders and messages at the operating system, browser or cloud level. A user's contacts can be organized by importance or by groups. For example, the CEO of the company a user works for and a user's child care giver could both be set to critical. A user's contacts may also be grouped. Family members may be in one group, important colleagues may be in a second group, and friends in a third group.

How do you think this would work? Specifically:

A user's contacts can be organized by importance or by groups. For example, the CEO of the company a user works for and a user's child care giver could both be set to critical. A user's contacts may also be grouped. Family members may be in one group, important colleagues may be in a second group, and friends in a third group.

And

Example User Experience: Question for the group. How would data be shared, if at all, between applications containing, for example, contacts and the proposed mechanism

How does "The CEO of your company at facebook" gets reconciled with "The CEO of your company at your contacts list" and "The CEO of your company at linkedin"? That is, how do you know that they are the same entity/person? That is, facebook and linkedin and your contact list don't all share the same ID namespace, so how do you associate them into the same entity/person/id? For example, how does the user agent know that

https://www.facebook.com/sgoto
https://www.linkedin.com/in/samuelgoto
http://twitter.com/samuelgoto
http://github.com/samuelgoto

These are all the same person?

Start with section 2.2, “Reminders and Messages,” and review the questions about sharing contact data between applications. Investigate how Facebook, LinkedIn, Twitter, GitHub, and a contact list could identify the same person without a shared ID namespace; done requires a decided reconciliation approach documented for the proposed mechanism.