newline/form feed valid as attribute value?

Does anyone here know whether newlines, form feed or vertical feed are
valid within an attribute value (I hope not, otherwise it would make
it a lot harder to write a fast xml parser using regex alone)?

---------- Forwarded message ----------
From: Dan Shelton <>
Date: 1 July 2012 17:35
Subject: Re: newline/form feed valid as attribute value?
To: 


On 1 July 2012 17:06, Dan Shelton <> wrote:
> In which context are newlines valid values, i.e. is a newline
> character or a form feed a valid character in an attribute value?

Clarifying the question:
Is this a valid xml fragment:
-----cut-----
<mytag myattribute="hello
 world">sometext</mytag>
-----cut-----
Or as UNIX(TM) shell code:
/usr/bin/printf '/<mytag myattribute="hello \n world">sometext</mytag>'

Same with form feed:
/usr/bin/printf '/<mytag myattribute="hello \f world">sometext</mytag>'
Is this valid?

Or with vertical feed:
/usr/bin/printf '/<mytag myattribute="hello \v world">sometext</mytag>'
Is this valid?