Using Information Extraction for Question Answering

Done by

Rani Qumsiyeh

Problem

More Information added to the web everyday. Search engines exist but they have a problem

This calls for a different kind of search engine.

History of QA

QA can be dated back to the 1960’s

Two common approaches to design QA: Information Extraction Information Retrieval

Two conferences to evaluate QA systems TREC (Text REtrieval Conference) MUC (Message Understanding Conference)

Common Issues with QA systems

Information retrieval deals with keywords.

Information extraction learns the question.

The question could have multiple variations which meansEasier for IR but more broad resultsHarder for IE but more EXACT results

Message Understanding Conference (MUC) Sponsored by the Defense Advanced Research

Projects Agency (DARPA) 1991-1998.

Developed methods for formal evaluation of IE systems

In the form of a competition, where the participants compare their results with each other and against human annotators‘ key templates.

Short system preparation time to stimulate portability to new extraction problems. Only 1 month to adapt the system to the new scenario before the formal run.

Evaluation Metrics

Precision and recall: Precision: correct answers/answers produced Recall: correct answers/total possible answers

F-measure Where is a parameter representing relative

importance of P & R:

E.g., =1, then P&R equal weight, =0, then only P Current State-of-Art: F=.60 barrier

MUC Extraction Tasks

Named Entity task (NE) Template Element task (TE) Template Relation task (TR) Scenario Template task (ST) Coreference task (CO)

Named Entity Task (NE)

Mark into the text each string that represents, a person, organization, or location name, or a date or time, or a currency or percentage figure

Template Element Task (TE)

Extract basic information related to organization, person, and artifact entities, drawing evidence from everywhere in the text.

Template Relation task (TR)

Extract relational information on employee_of, manufacture_of, location_of relations etc. (TR expresses domain independent relationships between entities identified by TE)

Scenario Template task (ST)

Extract prespecified event information and relate the event information to particular organization, person, or artifact entities (ST identifies domain and task specific entities and relations)

Coreference task (CO)

Capture information on corefering expressions, i.e. all mentions of a given entity, including those marked in NE and TE (Nouns, Noun phrases, Pronouns)

An Example

The shiny red rocket was fired on Tuesday. It is the brainchild of Dr. Big Head. Dr. Head is a staff scientist at We Build Rockets Inc.

NE: entities are rocket, Tuesday, Dr. Head and We Build Rockets

CO: it refers to the rocket; Dr. Head and Dr. Big Head are the same

TE: the rocket is shiny red and Head‘s brainchild TR: Dr. Head works for We Build Rockets Inc. ST: a rocket launching event occurred with the various

participants.

Scoring templates

Templates are compared on a slot-by-slot basisCorrect: response = keyPartial: response » keyIncorrect: response != keySpurious: key is blank

• overgen=spurious/actual

Missing: response is blank

Maximum Results Reported

KnowitAll, TextRunner, KnowitNow Differ in implementation, but do the same

thing.

Using them as QA systems

Able to handle questions that produce 1 relationWho is the president of the US? “can

handle”Who was the president of the US in

1998? “fails”

Produces a huge number of facts that the user still has to go through.

Textract

Aims at solving ambiguity in text by introducing more named entities.

What is Julian Werver Hill's wife's telephone number? equivalent to: What is Polly's telephone

number?

Where is Werver Hill's affiliated company located? equivalent to: Where is Microsoft located?

Proposed System

Determine what named entity we are looking for using Textract.

Use Part of Speech tagging.

Use TextRunner as the basis for search.

Use WordNet to find synonyms.

Use extra entities in text as “constraints”

Example

Example

(WP who) (VBD was) (DT the) (JJ first) (NN man) (TO to) (VB land) (IN on) (DT the) (NN moon)

The verb (VB) is treated as the argument. The noun (NN) is treated as the predicate We make sure that position is maintained We keep prepositions if they have two nouns.

(president of the US) Other non stop words are constraints, i.e.,

“first”

Example

Anaphora Resolution

Use anaphora resolution to determine that landed is not associated with landed but wrote instead.

Use Synonyms

We use word net to find possible synonyms for verbs and nouns to produce more facts.

We only consider 3 synonyms as it takes more time the more fact retrievals we have to do.

Using constraints

Delimitations

Works well with Who, When, Where questions as named entity is easily determined.Achieves about 90% accuracy on all

Works less well with What, How questionsAchieves about 70% accuracy

Takes about 13 seconds to answer question.

Future Work

Build an ontology to determine named entity and parse question (faster)

Handle combinations of questions. When and where did the holocaust

happen?