SECTION 4 HIGHLIGHTS THE MANAGEMENT OF THE INTER-FORMANCE OF A SYSTEM...

9

.

E1: "in the early 1970s"; Category: TIME

Representing topics in terms of relevant concepts

E2: "Egyptian President Anwar Sadat"; Category: PERSON

E3: "Egypt"; Category: COUNTRY

and relations is important for the processing of ques-

E4: "BW stockpile"; Category: UNKNOWN

2 predicates: P1="validate"; P2="has"

tions asked within the context of a given topic. For

Predicate−Argument Structures

P1: validate

interactive Q/A, however, the ideal topic-structured

Reference 1 (definitional)

Egyptian President X

arguments: A0 = E2: Answer Type: Definition

Reference 2 (metonymic)

PROCESSING

A1 = P2: have

representation would be in the form of question-

arguments: A0 = E3

Reference 3 (part−whole)

A1 = E4

E5: BW program

answer pairs (QUABs) that model the individual

ArgM−TMP: E1: Answer Type: Time

segments of the scenario. We have currently cre-

Reference 4 (relational)

P3: admit

ated two sets of QUABs: a handcrafted set and

QUESTIONS

Definition Pattern: Who is X?

an automatically-generated set. For the manually-

Q1: Who is Anwar Sadat?

Pattern: When did E3 P1 to P2 E4?

created set of QUABs, 4 linguists manually gener-

Q2: When did Egypt validate to having BW stockpiles?

Pattern: When did E3 P3 to P2 E4?

ated 3210 question-answer pairs for each of the 8

Q3: When did Egypt admit to having BW stockpiles?

Pattern: When did E3 P3 to P2 E5?

dialogue scenarios considered in our experiments.

Q4: When did Egypt admint to having a BW program?

In a separate effort, we devised a process for au-

Figure 4: Associating Questions with Answers.

tomatically populating the QUAB for each scenario.

R

Question Generation: In order to automati-

In order to generate question-answer pairs for each

cally generate questions from answer passages, we

subtopic, we first identified relevant text passages in

considered the following two problems:

the document collection to serve as “answers” and

Problem 1: Every word in an answer passage

then generated individual questions that could be an-

can refer to an entity, a relation, or an event. In

order for question generation be successful, we

4

Initially,

P Q

contains only the seed relation. Additional

must determine whether a particular reference

relations can be added with each iteration.

is “interesting” enough to the scenario such that

termine the selection of the answer. The predi-

it deserves to be mentioned in a topic-relevant

cate

!

can be substituted by its nominalization

question. For example, Figure 4 illustrates an

of

8

is BW, the same argument is

since

O

<

8

transferred to

answer that includes two predicates and four

. The causality implied by the

entities. In this case, four types of reference are

answer from Figure 5 has two components: (1)

used to associate these linguistic objects with

the effect (i.e. the predicate

8

) and (2) the re-

sult, which eliminates the semantic effect of the

other related objects: (a) definitional reference,

used to link entity (E1) “Anwar Sadat” to a cor-

negative polarity item never by implying the

responding attribute “Egyptian President”, (b)

predicate

!

, obstacle. The questions that are

metonymic reference, since (E1) can be coerced

generated are based on question patterns asso-

into (E2), (c) part-whole reference, since “BW

ciated with causal relations and therefore allow

stockpiles”(E4) necessarily imply the existence

different degrees for the specificity of the resul-

of a “BW program”(E5), and (d) relational ref-

tative, i.e obstacle or deterrent.

erence, since validating is subsumed as part

We generated several questions for each answer

of the meaning of declaring (as determined by

passage. Questions were generated based on pat-

WordNet glosses), while admitting can be de-

terns that were acquired to model interrogations

fined in terms of declaring, as in declaring [to

using relations between predicates and their argu-

be true].

ments. Such interrogations are based on (1) as-

ANSWER

sociations between the answer type (e.g. DATE)

Egyptian Deputy Minister Mahmud Salim states that Egypt’s

enemies would never use BW because they are aware that the

and the question stem (e.g. “when” and (2) the

Egyptians have "adequate means of retaliating without delay".

Predicates: P’1=state; P’2 = never use; P3 = be aware;

relation between predicates, question stem and the

P’4 = have P"4 = "the possesion"

Causality:

words that determine the answer type (Narayanan

P"4 = "the possesion" = nominalization(P’4) = EFFECT(P’2(BW))

and Harabagiu, 2004). In order to obtain these

P’2(BW) = NON−NEGATIVE RESULT(P5); P’5 = "obstacle"

PROCESSING

specialization

Reference: P’1 P’6 = view

predicate-argument patterns, we used 30% (approxi-

mately 1500 questions) of the handcrafted question-

Pattern: Does Egypt P’6 P"4(BW) as a P’5?

Does Egypt view the possesion of BW as an obstacle?

answer pairs, selected at random from each of the 8

Does Egypt view the possesion of BW as a deterrent?

dialogue scenarios. As Figures 4 and 5 illustrate, we

Figure 5: Questions for Implied Causal Relations.

used patterns based on (a) embedded predicates and

Problem 2: We have found that the identifica-

(b) causal or counterfactual predicates.

tion of the association between a candidate an-

swer and a question depends on (a) the recogni-

4 Managing Interactive Q/A Dialogues

tion of predicates and entities based on both the

output of a named entity recognizer and a se-

As illustrated in Figure 1, the main idea of man-

mantic parser (Surdeanu et al., 2003) and their

aging dialogues in which interactions with the Q/A

system occur is based on the notion of predictions,

structuring into predicate-argument frames, (b)

i.e. by proposing to the user a small set of questions

the resolution of reference (addressed in Prob-

that tackle the same subject as her question (as illus-

lem 1), (c) the recognition of implicit rela-

trated in Table 1). The advantage is that the user can

tions between predications stated in the answer.

follow-up with one of the pre-processed questions,

Some of these implicit relations are referential,

8

8

<

as is the relation between predicates

and

that has a correct answer and resides in one of the

QUABs. This enhances the effectiveness of the dia-

illustrated in Figure 4. A special case of im-

logue. It also may impact on the efficiency, i.e. the

plicit relations are the causal relations. Fig-

ure 5 illustrates an answer where a causal re-

number of questions being asked if the QUABs have

lation exists and is marked by the cue phrase

good coverage of the subject areas of the scenario.

because. Predicates – like those in Figure 5 –

Moreover, complex questions, that generally are not

) or negative (like

can be phrasal (like

processed with high accuracy by current state-of-

).

Causality is established between predicates

8

the-art Q/A systems, are associated with predictive

and

8

’ as they are the ones that ultimately de-

questions that represent decompositions based on

similarities between predicates and arguments of the

as

,)

:

7

@

B

7

A

, where

?

6

:>/

?

6

CB

original question and the predicted questions.

=

D

(,7HG

<

:E

:>FN

%

E

The selection of the questions from the QUABs

E

6

F

BIKJLNM<OQP

MR

that are proposed for each user question is based on

Similarity Metric 4 is based on the question

a similarity-metric that ranks the QUAB questions.

type similarity. Instead of using the question

To compute the similarity metric, we have experi-

class, determined by its stem, whenever we

mented with seven different metrics. The first four

could recognize the answer type expected by

metrics were introduced in (Lytinen and Tomuro,

the question, we used it for matching. As back-