Book meme, per instructions :)

Following a fellow hackerette's instructions, here's my meme:

"Computer science has a subdiscipline called Information Retrieval 
(IR for short) that focuses almost entirely on this problem."

And the original Andreia's instructions copied here:

• Grab the nearest book.
• Open it to page 56.
• Find the fifth sentence.
• Post the text of the sentence in your journal along with these instructions.
• Don't dig for your favorite book, the cool book, or the intellectual one: pick the CLOSEST.

So, Andreia, what's the page number for next week? :)