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[XML-DEV Mailing List Archive Home] [By Thread] [By Date] [Recent Entries] [Reply To This Message] Re: ASN.1 is an XML Schema Language (Fix those lists!)and Bina
 Robin Berjon wrote: > Alessandro Triglia wrote: > >> Amelia A. Lewis wrote: >> >>> We believe in unicode and concrete syntax. >> >> >> Good. So you don't believe in schemas. That's fine. Just use XML 1.0. > > > I don't think that that happens to be what Amy said (apologies if I > presume wrong). The fact is that at this point in time any schema > language for XML defines one single concrete syntax. And a fair part of > what the ASN.1 people do not seem to understand is that the XML folks > see that as a *good* thing. > > The ASN.1 equivalent of a simple XML parser in terms of universality > would have to properly decode (and likely handle negotiation for) BER, > PER, CER, DER, XER, and probably LWER, OER, and SER. That's a bit of a > behemoth to implement! Nah, just BER. BER is the Basic encoding after all - any general ASN.1 tool will handle BER; the others are more optional. This really comes down to application profiles - IIRC, in the original use of ASN.1 as Layer 6 of the OSI stack, everyone HAD to support BER and could optionally support others. Although when people define a data structure in ASN.1 and then say "It must be encoded in PER", they then choose not to require their parsers to support BER - that's up to them, of course. But in any situation where more than one transfer syntax is allowed, BER should be one of them... Also, it's not as much of a problem as you imagine having all those different sets of encoding rules - since the code for each of them really only needs to be written once as part of the toolkit; from there on up, everything else can be syntax-agnostic. XML is even worse than ASN.1 in this respect, of course; XML is based upon "text", and there are myriad ways of representing this. An XML parser needs to understand (IIRC) US-ASCII, UTF-8, and UTF-16 or something like that, so it could well barf on something written in EBCDIC. So a truly universal XML parser really ought to support every encoding listed under: http://www.iana.org/assignments/character-sets XML is *not* a concrete syntax in terms of actual bytes on the wire, by any stretch of the imagination; it's concrete in terms of *characters*, but those "characters" are still abstract things in terms of bits on the wire. Anybody who is looking for a single concrete syntax ought to leave XML alone right now and try XDR (RFC1014; http://www.faqs.org/rfcs/rfc1014.html) ABS 
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