Within  a website, create user relationship types like "friends" in Facebook or Linked-in. Consider various levels of the user relationships (full, partial, minimal sharing of your user details with another user).

Relationships may also be one-way or mutual. If a relationship type is one-way (subscriber) only the requester is shown as relating to the requestee. Relationship types can also be set as needing or not needing approval, and to auto approve relationships on a per-relationship type basis.

The following functionalities can also be integrated:

• conditionally send email notifications regarding relationship creation, removal, approval, disapproval and cancellation
• creates default relationships to any user joining the site
• invitations capability and allows users to specify a relationship to a user that they invite to join the site
• private messaging showing your relationships in the quick select list (see private messaging here)
• users can send a message with their relationship request to another user
• access or restriction to access of site content based on relationships