There is a high likelihood that many PDS systems will provide other services to the user, and thus are likely to have other information about the user such as language, country, etc. When the user signs up for that PDS offering, the service provide can list the attributes that it knows about the user that it thinks the user is likely willing to make public, and then ask the user to confirm they are in fact okay with sharing that information. For common attributes that the service provider does not know, it could prompt the user.