A system for building a database that stores information representative of the organizational structure of a community of users of a computer network is disclosed. The system uses an online computer applications service that facilitates the initiation and completion of transactions between users in the community. Initially, a first user from the community registers on the computer applications service and information representative of the first user is stored in the database. Next, a first transaction record is created in the database from information inputted by the first registered user. The first transaction record includes at least one field representing an identity of a first unregistered user in the community, a field representing a role of the first registered user in the first transaction, and a field representing a role of the first unregistered user in the first transaction. After creation of the first transaction record, the first unregistered user is invited to register with the service when information representative of the first transaction is sent to the first unregistered user. In response to this invitation, the first unregistered user registers with the service and information representative of the first unregistered user is stored in the database, thereby transforming the first unregistered user into a second registered user. After registration of the second user, further users from the community are invited onto the service and registered on the database by repeating the above process.