Slide 9 of 41
Notes:
Specifications using this approach typically had text describing the way in which ID parts (sometimes called the type part) are encoded, and the way in which length fields are encoded, leaving only the encoding (and meaning) of the value part of each parameter to be specified separately.
The parameters of each message were then specified by a table which listed each parameter in turn, giving:
- the ID code
- the length (if of fixed length)
- whether it is optional or mandatory to include it in the message
- the semantics (and if necessary encoding) of the value part
This approach is often called the tabular notation approach to protocol definition. This approach does made it easier to provide some tool support for implementors, with common subroutines to encode Ids and lengths, but the support is necessarily very limited.
Again, there are many different variants of this sort of notation, and the tabular format is hard for a computer to read.
