Google Contacts: Unique Contacts?

I am building an application that I will need to distinguish the Google Contacts from each other. I am just wondering, as long as google sends contacts as First Name/Last Name/mail.. etc (Example) without a unique ID, what will be the first approach to distinguish each contacts?

1) Should I create an ID based on the user's fields? -> by a minimal change, it can break down.

2) Should I create an ID based on First Name开发者_开发知识库 + Last Name? -> but most people can have duplicate contacts on their page, would that be a problem? Or married contacts, which can create a little mess.

The reason I am asking this I am trying to create relations and I need to store the data somewhere like that [person=Darth Vader, subject=Luke Skywalker, type=father(or son)], so I need a fast algorithm that can make a mapping for each contact and retrieve the related contacts fast.

I believe they do send back an ID. From the return schema:

<link rel='self' type='application/atom+xml' href='https://www.google.com/m8/feeds/contacts/userEmail/full/contactId'/>

You could use the full HREF value as the ID, or parse out the contactID from the end of the URL, whichever you like better.