xml-dev - Re: ASN.1

[David Brownell <david-b@pacbell.net>]

> I would suggest to folks who need this level of data type reuse and/or
> sophistication that they look into ASN.1 ...  Perhaps most important,
> all datatypes defined using ASN.1 have a standard, unambiguous method of
> encoding the data for transmission on the wire.  These rules are known as
> the "Basic Encoding Rules", or BER, of ASN.1.

A handful of points there.  First, ASN.1 is generally accepted to be far
more complex than is justifiable for most applications.  Second, there
are multiple syntaxes (the newer one is more cryptic than the original).
Third, BER is not the only standardized encoding ... there's also DER, which
is a bit more widely used.  (X.509 certs use BER, but most everything else
uses DER ... think of BER as "canonical DER".)  Choices, choices.

And fourth, DER and BER are examples of a philosophy of protocol development
that's been largely discredited for mainstream applications:  "bitstuffing".
It was a design principle that bit efficiency was more important than time
spent to encode or decode ... perhaps understandable for systems using X.25
networks where you more or less paid by the byte, but not on a LAN or even
the Internet.  Many folk think DER/BER should be the first to be put against
the wall when the revolution (XML?) comes; they're that unpleasant to use.


> So, I would use ...
> ASN.1 based private protocol for custom application work.

At the risk of touching off a religious war, I'd not suggest anyone
inflict ASN.1 on themselves, ever!  Unless they're plugging into an
existing system based on it ... and even then, they should think about
whether it's practical to replace/supplant that existing system.

- Dave

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