I'm working on a forum application and have a couple of questions regarding semantics.

In the DB, we have a groups table and a group members table. Each group can have an owner. Would you state that the owner is in the group members table (with a group_membership_type attribute) OR would you say that it is already implied by the group_owner attribute in the group table?

Also, can a topic be considered a post or are they two separate things?