searching with autocompletion cool algorithms for a cool feature holger bast bast@mpi-inf.mpg.de

Searching with Autocompletioncool algorithms for a cool feature

Holger Bastbast@mpi-inf.mpg.de

A: 1,3,7,8B: 1,3,5,8,10C: 5,10D: 2,5,7,8

Ordinary Inverted Index

~ |W| time per query

Our new data structure

~ |W'| time per query

Doc 1

A BDoc 2

D

Doc 3

A BDoc 4

-Doc 5

B C D

Doc 6

-Doc 7

A DDoc 8

A B D

Doc 9

-Doc10

B CDCBA

A-D

A-B C-D

ADA B AA B111010110100110001000001

B B B 1010010111

CDDC00011110110

000 000 0000 1000

The core algorithmic problem

Given a range of words W (all completions of the last word the user has started typing)and a set of documents D (the hits of the preceding part of the query),

compute the subset W' W⊆ of words that occur in at least one document of D and the subset D' D⊆ of documents containing a word from W'.

For the queryadfocs rag

all words aredisplayed that start with ragand that occurin a document

that also containsa word startingwith adfocs.

This list ofcompletions is

updated with every new letteryou type!

The list of tophits is also

updated withevery new letter

you type.

It is oftensurprising howlittle one has totype to get towhat one was

looking for!

Please try ityourself on the

MPII homepage.

Type a ? for helpbefore you start

searching!

typically

|W'| << |W|