What these questions do not address is the much more difficult task of translating the semantics of library data into something new. It takes only a short investigation of the data coded in MARC21 to reveal that the tags and subfields themselves are inadequate to define the actual data elements carried in library catalog records, as Jason Thomale discussed in his recent article [1]. It is therefore logical that a first step in the transformation of MARC21 to another format (or formats, for there may be more than one) is to identify the data elements that are contained within the MARC21 record. That task, as Thomale evidenced in his example, is more difficult than it may seem.