What is the best metaphor of AND and OR for searching?

Question

As programmers, we are all aware of the differences between AND and OR (junction and union). I'm building a website that list properties and I'm really struggling on the search part. I want the user to be able to search using checkbox, but some criteria make more sense using AND and other using OR.

For example, show properties that have "4 bedrooms AND 2 bathrooms" and "near downtown OR near a bus transit".

Usually search are only junction (like Google), or they actually explain the use of AND or OR. But since my target audience is very broad, I'm looking for simple visual indicator that could be understood by any person, not those only mathematically inclined :).

Answer 1

I believe (most of) the users understand that when the:

<select>
  <option>...
  <option>...
</select>

is used, then all items are taken with OR.

I guess the natural way to have AND selections is to have a group of check-boxes.

Answer 2

When users select their options, You could simultaneously (ajaxly) write down a phrase in plain english.

This will allow the users understand you interface quite rapidly.

Answer 3

Why not just have your list of options and then have a checkbox that says 'Contains any of the above' (Or) and 'Contains all of the above' (And)

So:

 [ ] Option 1
 [X] Option 2
 [X] Option 3

[X]Contains all [ ] Contains any

This is a pretty simple way to convey and/or searching without getting too caught up in the logic behind it.