See this:
A Turing machine has an infinite tape that consists of adjacent cells
(or squares). On each cell is written a symbol. The symbols that are
allowed on the tape are finite in number and include the blank symbol.
Each Turing machine has it's own alphabet (i.e., finite set of symbols),
which determines the symbols that are allowed on the tape.
From the same site:
http://www.unidex.com/turing/tm_intro.htm
So, if XML disallows certain symbols, but each Turing machine has it's
own alphabet, just because XML doesn't allow 0x0000 doesn't mean that an
XSLT stylesheet can't be a UTM, just that it has a different alphabet
from another UTM. In fact, the other page -
http://www.unidex.com/turing/utm.htm - states that: The Universal Turing
Machine stylesheet runs the Turing machine that is SPECIFIED BY THE
SOURCE DOCUMENT.
Not some pie in the sky non-XML compliant other source document. A
Turing Machine has its own set of rules that it has to follow to get to
where it's going.
-------
Jerry
-----Original Message-----
From: Kenneth Stephen
[mailto:marvin(_dot_)the(_dot_)cynical(_dot_)robot(_at_)gmail(_dot_)com]
Sent: Friday, August 27, 2004 12:36 PM
To: xsl-list(_at_)lists(_dot_)mulberrytech(_dot_)com
Subject: [xsl] [slightly OT]Universal Turing machine in XSLT
Hi,
Found this on the web :
http://www.unidex.com/turing/utm.htm
It seems to me that one of the implicit assumptions used by a UTM
is that it is able to write any specified symbol. If I read the XML
spec correctly though, certain symbols are not legal (for example
0x0000 is not a valid Unicode codepoint). That being the case, can
this UTM really be valid?
Thanks,
Kenneth
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