1. The core algorithmic problem Ordinary Inverted Index
Searching with Autocompletion cool algorithms for a cool feature Holger Bast
For the query
adfocs rag
all words are
displayed that
start with rag
and that occur
in a document
that also contains a word starting
with adfocs.
This list of
completions is
updated with every
new letter
you type!
Please try it
yourself on the
MPII homepage.
Type a ? for help
before you start
searching!
The list of top
hits is also
updated with
every new letter
you type.
It is often
surprising how
little one has to
type to get to
what one was
looking for!
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'.
Our new data structure
~ |W'| time per query
typically
|W'| << |W|
Ordinary Inverted Index
~ |W| time per query D C B A
A-D
A-B
C-D
ADA B AA B
B B B
111
CDDC
0110
000
0000
1000
Doc 1
A B
Doc 2 D
Doc 3
Doc 4 -
Doc 5
B C D
Doc 6
Doc 7
A D
Doc 8
A B D
Doc 9
Doc10
B C
A: 1,3,7,8
B: 1,3,5,8,10
C: 5,10
D: 2,5,7,8