The foaf:plan property provides a space for a foaf:Person to hold some arbitrary content that would appear in a traditional '.plan' file. The plan file was stored in a user's home directory on a UNIX machine, and displayed to people when the user was queried with the finger utility.

A plan file could contain anything. Typical uses included brief comments, thoughts, or remarks on what a person had been doing lately. Plan files were also prone to being witty or simply osbscure. Others may be more creative, writing any number of seemingly random compositions in their plan file for people to stumble upon.

See History of the Finger Protocol by Rajiv Shah for more on this piece of Internet history. The foaf:geekcode property may also be of interest.