What Value is Used from Oracle Fusion to Initiate SSO with Federated Identity Provider

Summary:

I have an Oracle Fusion environment already working with SSO today. We currently are creating usernames with the company e-mail address. Currently e-mail addresses are recycled by the company and reused if someone with the same first initial and last name come back into the organization. Since we are using the e-mail address in the username field, this will pose a problem as soon as we have one of the re-use circumstances. We do find this to be an issue for certain parts of the work where common names are used over and over again creating these re-use scenarios.