In the DISCUSS logo pictured on the cover, the letters are linked together by chains. A ``chain'' is a set of transactions linked together by the same subject.
When a user enters a new transaction into a DISCUSS meeting, the user has the choice of starting a new chain or adding onto an existing chain. The ``talk'' command will prompt the user for a subject, and will enter the transaction as the start of a new chain. The ``reply'' command takes an already existing transaction, and adds the new transaction onto the old transaction's chain. The subject of this new transaction is formed by prepending ``Re:'' to the old subject. So a transaction chain roughly corresponds to a single conversation within the meeting.
DISCUSS provides commands that allow you to take advantage of the chaining structure. When DISCUSS prints a transaction, it displays the pref (previous reference) and nref (next reference) of that transaction. These are the previous and next transactions within the chain, respectively. By using these numbers, or taking advantage of the ``pref'' and ``nref'' transaction specifiers, you can travel through the chain and follow the particular conversation. Other chain-related transaction specifiers are ``fref'' and ``lref'', which refer to the beginning and end of the chain. Although the various clients have different names for these chaining commands, they all allow for such actions.