Solved

Can It Be In Horn Form

Posted on 2010-11-10
12
462 Views
Last Modified: 2012-06-27
I'm trying to understand whether R => (E <==> C) can be expressed in Horn form. How do I deal with this?
0
Comment
Question by:JCW2
  • 6
  • 6
12 Comments
 
LVL 37

Accepted Solution

by:
TommySzalapski earned 500 total points
ID: 34108276
For Horn form I make a truth table with each of the variables and the main clause I'm testing.
For all the Fs in the main clause column all the literals must be F in the same row except for one.
So your equations truth table looks like the following. Can it go into Horn form? Look at the F rows in the last column and tell me.
0
 

Author Comment

by:JCW2
ID: 34115019
By main clause, do you mean R?
0
 
LVL 37

Assisted Solution

by:TommySzalapski
TommySzalapski earned 500 total points
ID: 34115139
No. The main clause is R => (E <==> C)
The easiest way to set up the truth table would probably be to put columns for
R, E, C, E<==>C, and R=>(E<==>C)
Then circle all the rows with Fs in the last column. Ignore the E<==>C column when checking for Horn form of course. Just check the literals. I add that column because I don't want to try to do it all in my head.
Generate the truth table and post it so I can help you make sure you are doing it right. I'll be on for a couple hours yet.
0
 

Author Comment

by:JCW2
ID: 34115570
Using E <==> C as the main clause, I don't think I can express my problem in Horn form. Am I correct?
0
 

Author Comment

by:JCW2
ID: 34115580
Disregard the last comment.
0
 
LVL 37

Assisted Solution

by:TommySzalapski
TommySzalapski earned 500 total points
ID: 34115614
It is true that E<==>C cannot be expressed in Horn form. So you're probably doing it right.
0
Is Your Active Directory as Secure as You Think?

More than 75% of all records are compromised because of the loss or theft of a privileged credential. Experts have been exploring Active Directory infrastructure to identify key threats and establish best practices for keeping data safe. Attend this month’s webinar to learn more.

 

Author Comment

by:JCW2
ID: 34115701
From what I can see, the relevant rows are

T T F - F and
T F T - F.

Therefore, we can not express the propositional sentence in Horn form.
Is this correct?
0
 
LVL 37

Assisted Solution

by:TommySzalapski
TommySzalapski earned 500 total points
ID: 34115731
100% correct.
0
 

Author Comment

by:JCW2
ID: 34115794
Another thing: is it possible for a sentence to be expressed in Horn form if all literals are F in the proper row?
0
 
LVL 37

Assisted Solution

by:TommySzalapski
TommySzalapski earned 500 total points
ID: 34115925
Yes. Sorry. Should have read:

For Horn form I make a truth table with each of the variables and the main clause I'm testing.
For all the Fs in the main clause column all or all but one of the literals must be F in the same row.
0
 

Author Closing Comment

by:JCW2
ID: 34115958
Thank you for your help.
0
 
LVL 37

Expert Comment

by:TommySzalapski
ID: 34115981
A Horn clause has AT MOST one positive literal.
A definite clause has EXACTLY one positive literal.
So the definite clause would not work if the whole row was Ts, but Horn could.
0

Featured Post

Is Your Active Directory as Secure as You Think?

More than 75% of all records are compromised because of the loss or theft of a privileged credential. Experts have been exploring Active Directory infrastructure to identify key threats and establish best practices for keeping data safe. Attend this month’s webinar to learn more.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

This article is meant to give a basic understanding of how to use R Sweave as a way to merge LaTeX and R code seamlessly into one presentable document.
This article will show, step by step, how to integrate R code into a R Sweave document
Viewers will learn how to properly install Eclipse with the necessary JDK, and will take a look at an introductory Java program. Download Eclipse installation zip file: Extract files from zip file: Download and install JDK 8: Open Eclipse and …
In this fourth video of the Xpdf series, we discuss and demonstrate the PDFinfo utility, which retrieves the contents of a PDF's Info Dictionary, as well as some other information, including the page count. We show how to isolate the page count in a…

920 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question

Need Help in Real-Time?

Connect with top rated Experts

12 Experts available now in Live!

Get 1:1 Help Now