Character Encoding Detection

[Chris Hubick]

	I am new to Character Encodings, and am trying to implement them
for my XML parser.

As I understand it, UCS has two flavors, UCS-2 and UCS-4, either of which
can optionally have a UCS transformation applied to them.  It is my
understanding that you could author an XML document in either of these,
without applying a transformation.

The UTF-16 spec at:
	http://www.stonehand.com/unicode/standard/wg2n1035.html
states:
	"In UTF-16, any UCS character from the BMP shall be represented by
its UCS-2 coded representation."

Now in UCS-2:
	'<' is 00 3C
	'?' is 00 3f

So the start of a UCS-2 or UTF-16 encoded XML document would be 00 3C 00
3F

In the section on autodetection of character encodings the XML spec
states "00 3C 00 3F: UTF-16, big-endian, no Byte Order Mark (and thus,
strictly speaking, in error)"

	My question is, why is this an error rather than a perfectly
acceptable untransformed UCS-2 document?

<?xml version="1.0" encoding="ISO-10646-UCS-2"?>


---
Chris Hubick
mailto:chris at hubick.com
http://www.hubick.com/



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