XFN 1.1: A Comprehensive Guide to the XHTML Friends Network

The XHTML Friends Network (XFN), introduced in December 2003, provides a standardized method for representing human relationships using hyperlinks within HTML. Developed by the Global Multimedia Protocols Group (GMPG), XFN allows web authors to define the nature of their connections to others by adding specific keywords as the ‘rel’ attribute to their links. This guide details the XFN 1.1 profile, outlining the various relationship types and their characteristics.

What is XFN and Why Use It?

XFN, as described in HTML4 Meta data profiles, offers a standard way to communicate the nature of relationships between individuals online. By employing specific ‘rel’ values, users can convey the depth and type of connection they share with others, fostering richer social data and more meaningful connections within the digital space.

Understanding the ‘rel’ Attribute and XFN Values

The core of XFN lies in the use of the HTML ‘rel’ attribute. This attribute allows authors to specify the relationship between the current document and the linked document. XFN builds upon this by defining a set of standardized values to represent different types of relationships. Here’s a breakdown of the available values, categorized for clarity:

Friendship

• contact: Indicates someone you know how to get in touch with. Often symmetric.
• acquaintance: Represents someone you’ve exchanged greetings with, but not much more. Often symmetric.
• friend: Denotes someone you consider a friend – a compatriot or buddy. Often symmetric.

Physical Relationships

• met: Indicates someone you have met in person. Symmetric.

Professional Relationships

• co-worker: Represents someone you perform with or share an organization with. Symmetric and usually transitive.
• colleague: Indicates someone in the same field of study or activity. Symmetric and often transitive.

Geographical Relationships

• co-resident: Represents someone you share a street address with. Symmetric and transitive.
• neighbor: Indicates someone who lives nearby. Symmetric and often transitive.

Family Relationships

• child: A person’s genetic offspring or adopted child. Inverse is ‘parent’.
• parent: Inverse of ‘child’.
• sibling: Someone you share a parent with. Symmetric and usually transitive.
• spouse: Someone you are married to. Symmetric and not transitive.
• kin: A relative, someone you consider part of your extended family. Symmetric and typically transitive.

Romantic Relationships

• muse: Someone who brings you inspiration. No inverse.
• crush: Someone you have a crush on. No inverse.
• date: Someone you are dating. Symmetric and not transitive.
• sweetheart: Someone with whom you are intimate and at least somewhat committed. Symmetric and not transitive.

Identity

• me: A link to yourself at a different URL. Exclusive of all other XFN values. Required symmetric.

Key Concepts

• Symmetry: A symmetrical relationship means if ‘A rel B’ is true, then ‘B rel A’ is also true. For example, if Alice is a friend of Bob, then Bob is generally a friend of Alice.
• Transitivity: A transitive relationship means if ‘A rel B’ and ‘B rel C’ are true, then ‘A rel C’ is also true. For example, if Alice is a co-worker of Bob, and Bob is a co-worker of Charlie, then Alice is likely a co-worker of Charlie.

Implementing XFN in Your HTML

Implementing XFN involves adding the appropriate ‘rel’ attribute to your HTML links. For example:

<a href="http://jimmy.example.com/" rel="friend">Jimmy Example</a>

Multiple values can be used to indicate multiple relationships:

<a href="http://jimmy.example.com/" rel="friend met">Jimmy Example</a>

The Rise and Fall (and Potential Revival?) of XFN

While XFN was the first microformat and initially gained traction, its use has diminished with the rise of dedicated social networking platforms. However, the principles of semantic web and representing relationships remain relevant, and there’s potential for a revival as people seek more control over their online identities and connections.

Benefits of Using XFN (Even Today)

Despite its reduced prevalence, XFN still offers benefits:

• Semantic Clarity: Provides a clear and standardized way to define relationships.
• Decentralization: Allows individuals to define their own networks without relying on centralized platforms.
• Interoperability: Facilitates the exchange of social data between different websites.

Further information about XFN can be found at GMPG and Microformats Wiki.