Multiple Occurrence Fields in a Fielded Buffer

Any field in a fielded buffer can occur more than once. Many FML functions take an argument that specifies which occurrence of a field is to be retrieved or modified. If a field occurs more than once, the first occurrence is numbered 0, and additional occurrences are numbered sequentially. The set of all occurrences makes up a logical sequence, but no overhead is associated with the occurrence number (that is, it is not stored in the fielded buffer).

If another occurrence of a field is added, it is added at the end of the set and is referred to as the next highest occurrence. When an occurrence other than the highest is deleted, all higher occurrences of the field are shifted down by one (for example, occurrence 6 becomes occurrence 5, 5 becomes 4, and so on).