(or, the OPH is not required to deal with such operations). The maximum length of the parSet of any encoded ASP is less than 256 octets. All bits in the message that are not used shall be set to binary 0. 5.7 Protocol Specification Methods Questions Used (yes/no)? Size/Range/Value INVid Operation classes: -REQUEST -ORDER -OFFER -INVITE -C_REPORT -U_REPORT Synchronous op. Asynchronous op. Destructive op parSet length in octets Spares Fig. 5.49 Constraints to the universal format as input to the intelligent format generator Given these prerequisites, the format generator then suggests a specialization of the universal format, see Fig. 5.50. ::= $INT SIZE (16) ::= $INT SIZE (64) ::= $BITSTR SIZE (1) aspPDU MTid ::= '0'B errrorPDU MTid ::=''1'B PrimType ::= $ENUM{request(0), confirm(1), refuse(2),order(3)} ASpid ::= SEQUENCE(PSid, $SPARE0 SIZE (3), OPid, PrimType} UniPdu ::= $CHOICE{AspPdu, ErrorPdu} AspPdu ::= $SEQ {{aspPDU}, asp ASPid, parSetLength $INT SIZE (256), parSet ANY DEFINED BY asp} ErrorPdu ::= $SEQ {{errorPDU}, cause INT{unknownObj(1),unknownOp(2),parSetErr(3),errPrimType(4), {spare '000'B}} cause ASPid ErrorPdu parSetLength parSet max 258 octets AspPdu Fig. 5.50 A generated format 5 Protocol Network Modelling The format is described both textually and graphically in Fig. 5.50. Note that the format has only 12 bits more than the minimum number of bits to encode the events. The designer can now edit the format specification before it is compiled into MEH and ENC functions. 5.7.5 Private Data Types For most protocols, there is no need to use anything but standardized typing and encoding systems (ASN.1 IDL, etc.), as long as a compact encoding system like the one used for AML types is also available. However, in case specific needs exist, the message design methodology should allow designers to define their own data types and associated encoding methods. Assume, e.g. that you want to encode a string of characters according to the IA5 alphabet (7-bit code). You may define the string as IA5String which refers