Reyyan Yeniterzi

Weakly-Supervised Discovery of Named Entities

Using Web Search Queries

Marius Pasca Google

CIKM 2007

Motivation

Name entities essential during the construction of

knowledge bases from Web helpful in various NLP tasks; like parsing,

coreference resolution … constitute a significant part of the Web

search queries helpful in building verticals in Web search

Previous works

Mining query logs to improve various IR tasks

re-ranking of retrieved documents query expansion spelling correction

Large-scale IE mainly on document collections ignoring the collective knowledge embedded

in noisy search queries This is the first work that applies name

entity finding to Web search query logs

Extraction from Query Logs

Given A set of target classes A set of seed instances

The goal To extract relevant class instances from

query logs Without using

Any domain knowledge Any handcrafted extraction pattern

Overview of the System

Step 1: identification of query templates that match the seed instances

Step 2: identification of candidate instances

Step 3: internal representation of candidate instances

query: prefix candidate_instance postfix entry: prefix postfix

weight of an entry = frequency of the query

Step 4: internal representation of seed instances

introducing weak supervision in the extraction process

the vectors associated with the seed instance are merged into a reference search-signature vector

a loose search fingerprint of the desired output type with respect to the class

Step 5: instance ranking

ranking based on the similarity score (computed with Jensen-Shannon) between each candidate vector and class vector

Reference search-signature vectors A series of queries that can be asked about

instances of a class

Given a set of candidate phrases, the system guess which candidate phrases are more likely to belong to the target class by looking at the queries

Experimental setting - 1

Target Classes 10 classes with 5 seed instances for each class

City Country Drug Food Location Movie Newspaper Person University VideoGame

Experimental setting - 2

Data A random sample of 50 million unique fully-

anonymized queries submitted to Google

Evaluation Procedure Top 250 candidates of each class are manually

assigned a correctness label 1 : correct 0 : incorrect

Precision at rank N has been calculated for several N values

Quality of Extracted Instances

Does the popularity of seed instances in query logs correlated with precision?

-0.17 -0.19

more queries with

seed instances

more accurate scoring

better internal representation

?

Comparing the usefulness of query logs vs. Web documents in NE finding

M. Pasca. Acquisition of categorized named entities for Web search. CIKM 2004 Target classes are incrementally

acquired from Web documents along with their respective instances by using hand crafted extraction patterns (D-patt) Class [such as|including] Instance

Manual one-to-one mapping of chosen target classes with acquired classes

Comparing the usefulness of query logs vs. Web documents in NE finding

Instances extracted from Web documents are also manually evaluated as correct and incorrect

Except City, Newspaper and Country classes, seed based extraction from queries outperformed D-patt in every other class

Conclusion

Search queries, which are thought as noisy, keyword based approximations of underspecified user information needs, proved to be useful in name entity discoveries even with a small set of seed instances with absolute precision (or precision improvement

relative to web based hand crafted system) 0.96 (29%) for prec@50 0.90 (26%) for prec@150 0.80 (15%) for prec@250

Questions ?