Opaque Message Parsing

A computer-implemented method of parsing a message comprising a sequence of data fields, the method comprising evaluating program code for processing the parsed message to identify a first set of data fields of the message that are referenced in said program code; identifying the boundaries of the data fields in a schema defining the format of said message; identifying a second set of data fields in said schema related to the first set of data fields by reference, said second set further including the first set; and sequentially parsing the message using the identified data field boundaries, wherein said parsing step comprises skipping data fields in said sequence that precede the first data field belonging to the second set. A computer program product comprising program code for implementing this method and a data processing system adapted to implement this method are also disclosed.