1. A computer-implemented method comprising: in response to a first user's data being stored in an archive, which contains first data available to the first user and not available to a second user and second data available to the second user and not available to the first user, identifying whether the first user's data pertains to a common topic; determining whether the first user and the second user have communicated and determining whether the first user and the second user have communicated about the common topic; based on the determination, sending an introduction to the first user that a) indicates that particular data not available to the first user and pertaining to the common topic is accessible upon request, b) identifies the common topic and c) identifies the second user; receiving, from the first user and in response to the introduction, a request to access the particular data not available to the first user and pertaining to the common topic; and enabling the first user and the second user to communicate about the common topic based on identifying, in the first data available to the first user and not available to the second user, and in the second data available to the second user and not available to the first user, the data pertaining to the common topic.