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Serialisation of PXP DTDs
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Date: 2008-10-24 (21:39)
From: Mauricio Fernandez <mfp@a...>
Subject: Re: [Caml-list] Re: Serialisation of PXP DTDs
On Fri, Oct 24, 2008 at 11:11:10AM +0200, Mikkel Fahnøe Jørgensen wrote:
> I guess this discussion is an overkill for the problem at hand, but
> speaking of binary extensible protocols, have you looked at ASN.1? It
> is an abstraction over any number of encodings. At least one binary
> encoding has extension bits to allow future growth of object
> collections and similar.

Yes, I referred to it indirectly in my previous message. Indeed, ASN.1
supports disjoint unions ("tagged types") that would allow to extend a type.
It is obviously possible to build extensible protocols with ASN.1, but if I
understand it correctly, not all protocols expressed in ASN.1's abstract
syntax are automatically extensible --- it requires some care when designing
them (i.e., tagging).

My main problem with ASN.1 is that even the distinguished encoding rules are
fairly complex; also, explicit tagging results in relatively heavy
serialization too. My protocol family is both substantially simpler and better
adapted for extensibility. For example, the generic pretty-printer (able to
decode any message) takes ~40 lines of code.

Mauricio Fernandez  -