boolean operations

vgurgov

Hi,

I am writing a small search engine with 3 search fields and "AND/OR" boolean operation in between each one.

So, there are 3 text fields and "AND/OR" radio buttons in between each text field.

Now, is there a general case of how a computer understands boolean operations, so that no matter what boolean operation the user will choose, the computer will more or less give the right results?

For example, if I am searching for "boy or girl and school", the computer should return me all the results containg the word "boy" or "girl", and "school" must also appear. If I enter "school and boy or girl", should it also return the same results? or is that a different search query altogether?

Basically, I am looking for a general case of where to put the parenthesis (I guess).

Thanks in advance!

klik

Are you talking about operator precedence?

'Boy or girl and school'

And has a higher precedence than or.

So this would return (all boys) and also would return (girls and school)

'School and boy or girl'

This would return (school and boy) and also would return (all girls)

vgurgov

Thank you for that klik,

I see what you are saying, but don't you think that to a regular user the search query 'Boy or girl and school' would mean to get all "boys" or "girls" and then return all that appear with "school"?

I am thinking it would be logical to put a set of parenthesis around the first 2 search queires to process them first (no matter what operator) and then to process third one?

I think that search query should be processed like this (notice the parenthesis):
(boy or girl) and school

Do you think it's safe to assume this for every possible query?

Weedpacket

Shouldn't boy or girl and school give the same results as school and boy or girl?

vgurgov

I think I solved my problem...
I noticed that I needed to process the queries with OR first, so I just put parenthesis around the OR pair (only when OR occurs once). For other cases (when there are exactly 2 ANDs or 2 ORs or 1 AND or 1 OR) I left those untouched and it seems to give me the right output.

Thanks guys