Hi,
your explanation isn't really very clear. First you talk about
language theory, and then you talk about Boolean logic. 'or'
frequently works differently in natural language and boolean logic.
Your example 'coffee, tea or milk' is similar to a classic example
from philosophy courses of inclusive or, rather than the exclusive or
you claim. The situation is this: a philosopher asks his guest what
he'd like to drink. The guest replies 'tea or coffee'. The philosopher
returns with a cup containing both tea and coffee. This demonstrates
several things, including:
1. philosophers are not comedians
2. the same term does not necessarily mean the same thing in natural
language and technical language
3. always ask for gin
In Boolean logic inclusive or (OR) and exclusive or (XOR) are derived
from set theory.
Consider 2 sets, A and B.
x is an element of A OR B if and only if x is in the union of A and B.
x is an element of A XOR B if and only if x is an element of the union of A and B and
not
in the intersection of A and B.
Your torture example is not exclusive because it could happen, and
frequently has, that a person reveals the code and still gets
tortured. It also occasionally happens that they neither get tortured
nor reveal the code - for example when James Bond abseils down the
wall and swings in through the window to rescue the prisoner and kill
the would-be torturer. It's an example of the informality & imprecision
of natural language.
Your instruction to a boolean search engine is incomplete and
inaccurate. It would not find pages which contain only 'junk'.
It would probably have to be something like this:
'(nikon or junk) and (not(nikon and junk))'
assuming they don't have an xor operator, which would allow
'nikon xor junk'.
---
Bob
mailto:[EMAIL PROTECTED]
Tuesday, April 24, 2001, 7:49:01 PM, you wrote:
> I'm glad you noted the smiley, Mark.
> For the record:
> In language theory, there are two kinds of OR:
> 1. exclusive, or alternative:
> "Do you prefer Nikon cameras or Pentax?"
> "Shall I torture you, or will you reveal the code?"
> "Coffee, tea, or milk?"
> 2. includive, or Boolean: "Find every web page that has Nikon OR junk." So
> instructed, a highly Boolean search engine such as Alta Vista will will
> return three kinds of pages:
> a. Nikon cameras are swell.(only Nikon)
> b. Junk in, junk out. (only junk or its case variants)
> c. Nikon cameras are junk. (both character strings permitted).
> If you wanted ONLY Nikon, or ONLY junk, you would have to instruct Alta
> Vista to search for
> Nikon AND NOT junk.
> This particular example, however, could pose a problem: I'm not sure how
> well Alta Vista handles oxymorons.
-
This message is from the Pentax-Discuss Mail List. To unsubscribe,
go to http://www.pdml.net and follow the directions. Don't forget to
visit the Pentax Users' Gallery at http://pug.komkon.org .
