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John Cowan wrote:
> Alaric B Snell scripsit:
> > The ASN.1 'equivelant' of a normal XML parser would just need to
> > support
> > BER, which is the current conventional "minimal" encoding. An ASN.1
> > toolkit that supported "BER, PER, CER, DER, XER, and
> probably LWER, OER,
> > and SER" would be more closely related to an XML parser
> that supported
> > US-ASCII, UTF-8, UTF-7, UTF-16, EBCDIC, ISO-8859-[1..15],
> > Baudot, etc...
> Hardly. Except for some feedback from the encoding
> declaration, which can be handled by a sniffer, charset
> decoding is a completely separate layer from parsing in XML.
I agree with you here.
This has the following implication: When using BER or PER, you don't need
to understand many different possible character encodings. When using XER,
you do, because the encoding is XML 1.0.
> The differences between BER, PER, and XER parsing are so
> profound as to cause the three parsers to have essentially
> nothing in common.
> When using XER, is one constrained to a specific encoding?
Yes and no. Encoders must use UTF-8, but there is a requirement for
decoders to be "non-validating XML processors", which implies a requirement
for understanding both UTF-8 and UTF-16.
> Also, I'm curious about which encoding-rules transformations
> one can perform without knowledge of the schema:
> BER to PER?
> XER to PER?
> BER to XER?
> XER to BER?
None. You always need the schema.
For parsing PER you absolutely need the schema. For *parsing* BER you don't
need the schema, but there is very little you can do with it without the
schema, especially when "implicit tagging" is used.
For parsing XER, you don't *need* the schema. Using ASN.1 with XML is much
like using XML Schema - you can use the schema either just for validation
purposes or for generating program structures to support data binding.
> I suggest you call for help, John Cowan
> or learn the difficult art of mud-breathing.
> --Great-Souled Sam
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