1. A method performed in a computer, for processing metadata, the method comprising: identifying a plurality of occurrences of a second abstract data type embedded within a first abstract data type; and generating, for the first abstract data type, a first description comprising a second description of the second abstract data type, and a plurality of offsets that identify a common position of said second description within said first description; wherein each offset is located in the first description in correspondence with an occurrence of the second abstract data type in the first abstract data type.