So far, we’ve looked into how to represent people in your application (and, perhaps more important, how to enable people to represent themselves), and we’ve examined the sort of activities people can do by touching social objects within your system. This brings us smack into the realm of relationships.

Without relationships between and among people, there is no social. Shared activities, like many of those discussed in Part III, naturally lead to the development of relationships in the real-world sense of the term: people meet through shared affinities, engage in activities together, date one another, make commitments to one another, and eventually find that they are in some sort of ongoing relationship.

In this part, we look at the mechanisms for labeling and declaring relationships, the community dynamics that can arise from multiple overlapping relationships (and, particularly, how to encourage healthy behavior and discourage parasites and vandals), and how to provide people with the means to bring their virtual connections into the real world through local engagement and shared event creation.