The migration scripts provided for the bboard forum by Musea take care of these problems.
You configure one database pool to point at your old installation. Then you run a series of scripts that pull data from the old installation, massage it, and stuff it into the new installation.
The scripts include one which defines several mapping tables. Using users as an example, a user is pulled from the old installation and created in the new installation. The old user_id and new user_id are added to a mapping table. Then as each forum post is migrated, the old user_id that points to the person who made the post is replaced with the new user_id in the OpenACS 4 installation.
This mapping is done for forums, bboard categories, and messages themselves.
The only thing not done at the moment is to examine each post to see if someone cleverly included a reference to another post via URL. If we want to maintain those someone will need to sit down and write a nice regexp to look for the old URLs, parse out the topic_id and message_id fields, and replace them with the new, mapped versions and the correct OpenACS 4 forum URL.
