Friday, February 27, 2009

Information exchange and encoding messages

For the encoding of messages to be exchanged in automation systems the red pencil tactics are still too often used, in the opinion: The shorter the message, the better. Is that what we really are looking for? Read the imposing joke on encoding.

Saving a few octets was one of the objectives of the definition of hundreds of solutions for communication protocols for automation systems - focusing on getting rid of some octets. Now with the use of secure TCP/IP based communication tunneling the many "old" protocols adds many times more octets at several layers than those saved in the  design of the "optimized" application protocols. Saving a few octets in the application protocols has a negligible effect! Some people that complained about the ASN.1 BER encoding years ago are now asking for Webservices with XML encoding - increasing the message lengths by orders of magnitude!

For every problem there is a solution which is simple, neat and wrong.

One lesson learned is: Focus on the applications, information to be exchanged, information exchange services, and the engineering process to get interoperable devices that can smoothly inter-operate - don't discuss saving a few bits in the application protocol encoding.

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