Writers of specifications and evaluators of vendor responses often have difficulty with the term "transaction" when seeking to set a level of throughput for an automated library system. The following is one of the simplest, most understandable, definitions we have found. It is contained in the product literature of the Digital Equipment Corporation. "A transaction is a series of actions in a computer that can only be treated as a single entity because all parts must take place or nothing takes place. It is not meaningful to define transactions in computer terms; it must be done in terms of the application." For example, in a circulation charge, there are several steps, but the charge is not completed until all related steps result in the updating of the files so that the system is capable of subsequent transactions such as overdue notice preparation, check-in, etc.