chunyi peng, zaoyang gong, guobin shen microsoft research asia hotweb 2006 measurement and modeling...
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Chunyi Peng, Zaoyang Gong, Guobin shenMicrosoft Research AsiaHotWeb 2006
MEASUREMENT AND MODELING OF A WEB-BASED QUESTION ANSWERING SYSTEM
Solve it yourself! – Ooh, out of our scope! Usually, Search it! –A common and good
way in many cases, but Search engine typically returns pages of links,
not direct answers. Some time it is very difficult for people to
describe their questions in a precise way. not all information is readily available in the
web. So, Ask! –A natural and effective way
Question-Answering (QA) utilizes grassroots intelligence and collaboration
Especially as a specific information acquisition.
When you have a question…
So, our goals…
Measurement and modeling o f a real large-scale QA system how a real QA system works? What are the typical user behaviors and
their impacts? Seek Better QA system
How to design a QA system? How to make performance tradeoffs?
iAsk (http://iask.sina.com.cn)
A topic-based web-QA system Question lifecycle:
questioning->wait for reply -> confirmation (closed)
Provide optimal reply selection & reply rewarding
Measurement Results
Data Set 2-month (Nov 22, 2005 to Jan 23, 2006) 350K questions and 2M replies 220K users, 1901 topics
Measurement on Question/reply patterns over time Question/reply pattern over topics Question/reply pattern across users Question/reply Incentive mechanisms
Behavior Pattern over Time
On Hourly Scale: a consistent usage pattern
Behavior Pattern over Topics Topic characteristics
P--Popularity (#Q) (Zipf-Popularity) questioning and replying activities
Q--Question Proneness (#Q/#U) the likelihood that a user will ask a question
R-- Reply Proneness (#R/#U) the likelihood that a user will reply a question
Our measurement shows that topic characteristics vary intensively and user behaves quite differently.
Behavior Pattern across Users Active and non-active users
about 9% users to 80% replies VS.about 22% users to 80% questions
asymmetric questioning/replying pattern 4.7% altruists VS. 17.7% free-riders
Narrow user interests #topic (Q): 1.8 #topic (R): 3.3
Performance Metric
Reply-Rate how likely his question can be replied
Reply-Number How likely his question can get an expected
answer
Reply-Latency how quickly he can get an answer
iAsk performance
Long-term performance: Reply-Rate: 99.8% Reply-Number: about 5 Reply-Latency: about 10hr
Within 24hrs Reply-Rate: 85% Reply-Number: about 4 Reply-Latency: about 6hr
In summary, the performance is quite satisfactory except sometimes users need tolerate a relative long delay
Measurement on Incentive Mechanism
Modeling
The question arrival distribution: Poisson distribution
The reply behavior: an approximate exponentially-decaying model
Performance formula Define dynamic performance
Parameter Impact
Possible Improvement
Active or Push-based Question Delivery Better Webpage Layout, e.g. adding
shortcuts Better Incentive mechanism Utilize Power of Social Networks
Conclusions
Web-QA that leverages the grassroots’ intelligence and collaboration is hot and getting hotter…
Our measurement and model revealed that the QA’s QoS heavily depends on three key factors: user scale, user reply probability and a system design artifact, e.g. webpage design.
Current simple Web-QA System achieved the acceptable performance, but there still is improvement room
Backup
Behavior Pattern over Topics Topic characteristics
P--Popularity (#Q) (Zipf-Popularity)
Behavior Pattern over Topics Topic characteristics
P--Popularity (#Q), Zipf-Popularity Q--Question Proneness (#Q/#U) R-- Reply Proneness (#R/#U)
Narrow User Interest Scope
Reply distribution (measured)
Static Performance Formula
Reply-Rate
Reply-Number
Reply-Latency
Dynamic Performance FormulaDefine dynamic performance
We have,
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