Complex sentence: The sequence of descriptors in Section 3 could be understood as the template of the BUFR message, in the sense that it contains the information necessary to either build or deconstruct the data values encoded in the matching bit-stream that is found in Section 4.
Split into simpler sentences: The sequence of descriptors in Section 3 could be understood as the template of the BUFR message. It contains the information necessary to either encode or decode the data values embedded in the matching bit-stream that is found in Section 4.