Officially Defined

• binary (RFC 4522)
• lang-* (RFC 5646)

General Use Cases

• Preferred Value
• Privacy Settings
• Role-Level Related Attributes
• Self Asserted Attributes
• Terms of Use
• Type of Use (eg: mail;x-student)
• Marking verified mail addresses (eg: mail;x-verified)

Current Implementations In The Wild

• New York University
• Umeå University