An Introduction to Information Retrieval and Question Answering Jimmy Lin College of Information Studies University of Maryland Wednesday December 8 2004 The Information Retrieval Cycle Source Selection Resource Query Formulation Query Search Ranked List Selection query reformulation vocabulary learning relevance feedback source reselection Documents Examination Documents Delivery Supporting the Search Process Source Selection Resource Query Formulation Query Search Indexing Acquisition Collection Index Ranked List Selection Documents Examination Documents Delivery Types of Information Needs Ad hoc retrieval find me documents like this Identify positive accomplishments of the Hubble telescope since it was launched in 1991 Compile a list of mammals that are considered to be endangered identify their habitat and if possible specify what threatens them Question answering Who discovered Oxygen When did Hawaii become a state Factoid Where is Ayer s Rock located What team won the World Series in 1992 What countries export oil List Name U S cities that have a Shubert theater Definition Who is Aaron Copland What is a quasar IR is an Experimental Science Formulate a research question the hypothesis Design an experiment to answer the question Perform the experiment Compare with a baseline control Does the experiment answer the question Are the results significant Report the results Rinse repeat What experiments Example questions Corresponding experiments Does morphological analysis improve retrieval performance Does expanding the query with synonyms improve retrieval performance Build a stemmed index and compare against unstemmed baseline Expand queries with synonyms and compare against baseline unexpanded query What s missing here IR Test Collections Three components of a test collection Collection of documents corpus Set of information needs topics Sets of documents that satisfy the information needs relevance judgments Metrics for assessing performance Precision Recall Other measures derived therefrom Where do they come from TREC Text REtrieval Conferences Series of annual evaluations started in 1992 Organized into tracks Test collections are formed by pooling Gather results from all participants Corpus topics judgments can be reused Roots of Question Answering Information Retrieval IR Information Extraction IE Information Retrieval IR Can substitute document for information IR systems Use statistical methods Rely on frequency of words in query document collection Retrieve complete documents Return ranked lists of hits based on relevance Limitations Answers questions indirectly Does not attempt to understand the meaning of user s query or documents in the collection Information Extraction IE IE systems Identify documents of a specific type Extract information according to pre defined templates Place the information into frame like database records Weather disaster Type Date Location Damage Deaths Templates pre defined questions Extracted information answers Limitations Templates are domain dependent and not easily portable One size does not fit all Central Idea of Factoid QA Determine the semantic type of the expected answer Who won the Nobel Peace Prize in 1991 is looking for a PERSON Retrieve documents that have keywords from the question Retrieve documents that have the keywords won Nobel Peace Prize and 1991 Look for named entities of the proper type near keywords Look for a PERSON near the keywords won Nobel Peace Prize and 1991 An Example Who won the Nobel Peace Prize in 1991 But many foreign investors remain sceptical and western governments are withholding aid because of the Slorc s dismal human rights record and the continued detention of Ms Aung San Suu Kyi the opposition leader who won the Nobel Peace Prize in 1991 The military junta took power in 1988 as pro democracy demonstrations were sweeping the country It held elections in 1990 but has ignored their result It has kept the 1991 Nobel peace prize winner Aung San Suu Kyi leader of the opposition party which won a landslide victory in the poll under house arrest since July 1989 The regime which is also engaged in a battle with insurgents near its eastern border with Thailand ignored a 1990 election victory by an opposition party and is detaining its leader Ms Aung San Suu Kyi who was awarded the 1991 Nobel Peace Prize According to the British Red Cross 5 000 or more refugees mainly the elderly and women and children are crossing into Bangladesh each day Generic QA Architecture NL question Question Analyzer IR Query Document Retriever Answer Type Documents Passage Retriever Passages Answer Extractor Answers Question analysis Question word cues Head noun cues Who person organization location e g city When date Where location What Why How What city which country what year Which astronaut what blues band Scalar adjective cues How long how fast how far how old Using WordNet What is the service ceiling of an U 2 length wingspan diameter NUMBER radius altitude ceiling Extracting Named Entities Person Mr Hubert J Smith Adm McInnes Grace Chan Title Chairman Vice President of Technology Secretary of State Country USSR France Haiti Haitian Republic City New York Rome Paris Birmingham Seneca Falls Province Kansas Yorkshire Uttar Pradesh Business GTE Corporation FreeMarkets Inc Acme University Bryn Mawr College University of Iowa Organization Red Cross Boys and Girls Club More Named Entities Currency 400 yen 100 DM 450 000 Linear 10 feet 100 miles 15 centimeters Area a square foot 15 acres Volume 6 cubic feet 100 gallons Weight 10 pounds half a ton 100 kilos Duration 10 day five minutes 3 years a millennium Frequency daily biannually 5 times 3 times a day Speed 6 miles per hour 15 feet per second 5 kph Age 3 weeks old 10 year old 50 years of age How do we extract NEs Heuristics and patterns Fixed lists gazetteers Machine learning approaches Answer Type Hierarchy Does it work Where do lobsters like to live Where do hyenas live near dumps in the dictionary Why can t ostriches fly in Saudi Arabia in the back of pick up trucks Where are zebras most likely found on a Canadian airline Because of American economic sanctions What s the population of Maryland three Limitations Conclusion Question answering is an exciting research area Lies at the intersection of information retrieval and natural language processing A real world application of NLP technologies The dream a vast repository of knowledge we can talk to We re a long way from there