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Author Topic:   The value of Gitt information
Percy
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Posts: 22388
From: New Hampshire
Joined: 12-23-2000
Member Rating: 5.2


Message 8 of 24 (329710)
07-07-2006 9:42 PM
Reply to: Message 7 by Cal
07-07-2006 12:21 PM


Cal writes:
Since Shannon was concerned with communications signals, his starting point was the tacit assumption that the message originated with an intelligent source;
I don't think Shannon made this assumption, even tacitly. If you read the original Shannon paper you'll see that he defines the communication problem as one of sending messages from a source to a destination. Each transmission sends one message from the message set. He states that meaning is not part of the communications problem (meaning would be associated with an intelligent source), and his definition of a message set does not specify an origin.
--Percy
Edited by Percy, : Fix typo.

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 Message 7 by Cal, posted 07-07-2006 12:21 PM Cal has replied

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 Message 9 by Cal, posted 07-08-2006 1:22 AM Percy has not replied

  
Percy
Member
Posts: 22388
From: New Hampshire
Joined: 12-23-2000
Member Rating: 5.2


Message 14 of 24 (330431)
07-10-2006 2:15 PM
Reply to: Message 13 by Cal
07-10-2006 1:44 PM


Cal writes:
What is a code? That which contains information.
Actually, a code is a set of rules for translating information from one form to another.
What is information? That which is represented by a code.
Actually, information is one of a set of messages that you wish to communicate. A code is how you transform that information into a form suitable for transmission.
What is DNA? Coded information.
That's correct.
But the only possible basis for regarding the bump in its original form as "signal", and the flat spot as "noise" would be that somebody or something cared what path the rock took.
This seems a leap of logic unrelated to anything else you said.
...Gitt's argument emerges as a Sunday-school-simple proposition: DNA is a message from God. I can't prove that false, and I won't waste a lot of energy trying. If your initial assumptions make you happy, who am I to screw with that?
I think few here would dispute someone's right to believe that DNA is a message from God. It only becomes a dispute when someone asserts that science says it is a message from God.
--Percy

This message is a reply to:
 Message 13 by Cal, posted 07-10-2006 1:44 PM Cal has replied

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 Message 15 by Cal, posted 07-10-2006 3:41 PM Percy has replied

  
Percy
Member
Posts: 22388
From: New Hampshire
Joined: 12-23-2000
Member Rating: 5.2


Message 17 of 24 (330532)
07-10-2006 4:50 PM
Reply to: Message 15 by Cal
07-10-2006 3:41 PM


Cal writes:
Well, if we want to be really pedantic, the strictest possible interpretation of Gitt might be said to include the implication that information (which cannot exist without a code, transmitter, etc) isn't actually information when it isn't being encoded, transmitted, or decoded. What it is the rest of the time, I can't imagine.
I wasn't saying anything about Gitt information. I don't know that a consistent and valid interpretation of it is possible - Gitt information seems to me just a bunch of unsupported assertions. The context of my reply was the encoding and decoding of Shannon information.
Actually, information is one of a set of messages that you wish to communicate.
Apologies for not finding that very... well, informative. "Wish" seems to be the key word there.
The principle that you find uninformative is at the core of Shannon information. This is from the 2nd paragraph of Shannon's original paper:
Shannon writes:
The significant aspect is that the actual message is one selected from a set of possible messages.
Moving on:
Cal writes:
I guess the whole metaphor must not have worked for you then. I don't have time to unpack it fully right now; maybe this evening. For now, I'll offer this hint: I'm suggesting that DNA transcription is, ultimately, as deterministic a process as is a rock rolling down a hill.
I think just your saying this clarifies your meaning, which at heart is about making an interpretation of which constitutes signal and which noise. But that involves assigning meaning, which as Shannon correctly states, is irrelevant to the engineering problem. Once you've made your choices about what constitutes signal and noise, then you can begin solving the information engineering problem.
--Percy

This message is a reply to:
 Message 15 by Cal, posted 07-10-2006 3:41 PM Cal has replied

Replies to this message:
 Message 18 by Cal, posted 07-11-2006 1:04 AM Percy has replied

  
Percy
Member
Posts: 22388
From: New Hampshire
Joined: 12-23-2000
Member Rating: 5.2


Message 19 of 24 (330700)
07-11-2006 3:28 AM
Reply to: Message 18 by Cal
07-11-2006 1:04 AM


Cal writes:
Percy writes:
I wasn't saying anything about Gitt information.
Oh, sorry. I guess I let the thread's title lead me astray.
Well, now I'm confused. Are you saying that when you wrote this in Message 13:
Cal in Message 13 writes:
My problem is in the circular way "information" is defined:
What is a code? That which contains information.
What is information? That which is represented by a code.
What is DNA? Coded information.
That you were talking about a problem with Gitt information, not Shannon information? It was written in response to a paragraph from WK about Shannon information.
If I axed you to relay a message for me, and it contained sum miss pelled words, would you have a reilable way of knowing whether those apparunt errors were kritical to the meaning of the "aksuall message"?
Yes, of course, but that's because of redundancy. The correct letters are only one of the many cues for the correct information.
Meaning isn't merely irrelevant to Shannon's purpose. It is assumed that among the set of all possible messages exists one which is the most meaningful,...
No, this is not assumed. As Shannon correctly states, meaning is irrelevant to the engineering problem.
...but it is not only unnecessary to choose between them on that basis, it is absolutely imperative that no attempt be made to do so; the message must be considered to have been at its maximum fidelity at the signal end.
My guess is that you're making the mistake of thinking that communicating information in the presence of noise is somehow associated with meaning. If an encoding of information contains insufficient redundancy such that after transmission through a noisy medium it is ambiguous which message from the set was originally sent, selecting a message from the set based upon some criteria is not an exercise where meaning has any role.
--Percy

This message is a reply to:
 Message 18 by Cal, posted 07-11-2006 1:04 AM Cal has not replied

Replies to this message:
 Message 20 by Wounded King, posted 07-11-2006 4:36 AM Percy has not replied

  
Percy
Member
Posts: 22388
From: New Hampshire
Joined: 12-23-2000
Member Rating: 5.2


Message 22 of 24 (330706)
07-11-2006 4:59 AM
Reply to: Message 18 by Cal
07-11-2006 1:04 AM


I think Message 20 from WK was intended as a response to you, not me.
--Percy

This message is a reply to:
 Message 18 by Cal, posted 07-11-2006 1:04 AM Cal has not replied

Replies to this message:
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