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Information Retrieval
Deepak Kumar
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Information Retrieval
Searching within a document collection for a particular information need.
• Traditional vs. web IR
•
•
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Query
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Search Engines…
AltavistaAskBaiduBingBlekkoChaChaDogpileDaumDuckDuckGo
EntirewebExciteFarooInfo.comGigablastGoogleGoHakiaHotBot
LeapfishLycosMonster CrawlerNaverOmgiliDmozScrub The WebSpezifyStinky Teddy
StumpdediaTeomaWebCrawlerYahoo! SearchYandex
![Page 5: Information Retrieval - cs.brynmawr.edu · Information Retrieval Searching within a document collection for a particular information need. • Traditional vs. web IR • • Query](https://reader034.vdocuments.site/reader034/viewer/2022042402/5f132190fbec4b05971e67b2/html5/thumbnails/5.jpg)
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Matching & Ranking
query
muddy waters
matched pages ranked pages
1.
2.
3.matching ranking
“hits”
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Index
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Inverted Index
• A mapping from content (words) to location.
• Example:
the dog stood on the mat
the cat stood while a dog sat
the cat sat on the mat
1 2 3
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Inverted Index
the dog stood on the mat
the cat stood while a dog sat
the cat sat on the mat
a 3cat 1 3dog 2 3mat 1 2on 1 2sat 1 3stood 2 3the 1 2 3while 3
1 2 3
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Inverted Index
the dog stood on the mat
the cat stood while a dog sat
the cat sat on the mat
a 3cat 1 3dog 2 3mat 1 2on 1 2sat 1 3stood 2 3the 1 2 3while 3
1 2 3
Every word in everyweb page is indexed!
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Searching
the dog stood on the mat
the cat stood while a dog sat
the cat sat on the mat
a 3cat 1 3dog 2 3mat 1 2on 1 2sat 1 3stood 2 3the 1 2 3while 3
1 2 3
query
cat
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Searching
the dog stood on the mat
the cat stood while a dog sat
the cat sat on the mat
a 3cat 1 3dog 2 3mat 1 2on 1 2sat 1 3stood 2 3the 1 2 3while 3
1 2 3
query
cat
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Searching
the dog stood on the mat
the cat stood while a dog sat
the cat sat on the mat
a 3cat 1 3dog 2 3mat 1 2on 1 2sat 1 3stood 2 3the 1 2 3while 3
1 2 3
query
cat
the cat sat on the mat
1
the cat stood while a dog sat3
hits
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Searching
the dog stood on the mat
the cat stood while a dog sat
the cat sat on the mat
a 3cat 1 3dog 2 3mat 1 2on 1 2sat 1 3stood 2 3the 1 2 3while 3
1 2 3
query
dog the cat stood while a dog sat3
hits
the dog stood on the mat2
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Searching
the dog stood on the mat
the cat stood while a dog sat
the cat sat on the mat
a 3cat 1 3dog 2 3mat 1 2on 1 2sat 1 3stood 2 3the 1 2 3while 3
1 2 3
query
cat dog
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Searching
the dog stood on the mat
the cat stood while a dog sat
the cat sat on the mat
a 3cat 1 3dog 2 3mat 1 2on 1 2sat 1 3stood 2 3the 1 2 3while 3
1 2 3
query
cat dog
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Searching
the dog stood on the mat
the cat stood while a dog sat
the cat sat on the mat
a 3cat 1 3dog 2 3mat 1 2on 1 2sat 1 3stood 2 3the 1 2 3while 3
1 2 3
query
cat dog
the cat stood while a dog sat3
hits
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Searching
the dog stood on the mat
the cat stood while a dog sat
the cat sat on the mat
a 3cat 1 3dog 2 3mat 1 2on 1 2sat 1 3stood 2 3the 1 2 3while 3
1 2 3
query
cat the sat ???
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Phrase Queries
the dog stood on the mat
the cat stood while a dog sat
the cat sat on the mat
a 3cat 1 3dog 2 3mat 1 2on 1 2sat 1 3stood 2 3the 1 2 3while 3
1 2 3
query
“cat sat”
the cat sat on the mat
1
the cat stood while a dog sat3
hits
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Phrase Queries
the dog stood on the mat
the cat stood while a dog sat
the cat sat on the mat
a 3cat 1 3dog 2 3mat 1 2on 1 2sat 1 3stood 2 3the 1 2 3while 3
1 2 3
query
“cat sat”
the cat sat on the mat
1
the cat stood while a dog sat3
hits
How to tell if two words occur next to each other?
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Phrase Queries
the dog stood on the mat
the cat stood while a dog sat
the cat sat on the mat
a 3cat 1 3dog 2 3mat 1 2on 1 2sat 1 3stood 2 3the 1 2 3while 3
1 2 3
query
“cat sat”
the cat sat on the mat
1
the cat stood while a dog sat3
hits
How to tell if two words occur next to each other? EFFICIENTLY???
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Inverted Index with Location
the dog stood on the mat
the cat stood while a dog sat
the cat sat on the mat
a 3‐5cat 1‐2 3‐2dog 2‐2 3‐6mat 1‐6 2‐6on 1‐4 2‐4sat 1‐3 3‐7stood 2‐3 3‐3the 1‐1 1‐5 2‐1 2‐5 3‐1while 3‐4
1 2 3
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Inverted Index with Location
the dog stood on the mat
the cat stood while a dog sat
the cat sat on the mat
a 3‐5cat 1‐2 3‐2dog 2‐2 3‐6mat 1‐6 2‐6on 1‐4 2‐4sat 1‐3 3‐7stood 2‐3 3‐3the 1‐1 1‐5 2‐1 2‐5 3‐1while 3‐4
1 2 3
query
“cat sat”
![Page 24: Information Retrieval - cs.brynmawr.edu · Information Retrieval Searching within a document collection for a particular information need. • Traditional vs. web IR • • Query](https://reader034.vdocuments.site/reader034/viewer/2022042402/5f132190fbec4b05971e67b2/html5/thumbnails/24.jpg)
Inverted Index with Location
the dog stood on the mat
the cat stood while a dog sat
the cat sat on the mat
a 3‐5cat 1‐2 3‐2dog 2‐2 3‐6mat 1‐6 2‐6on 1‐4 2‐4sat 1‐3 3‐7stood 2‐3 3‐3the 1‐1 1‐5 2‐1 2‐5 3‐1while 3‐4
1 2 3
query
“cat sat”
1‐2, 3‐2
1‐3, 3‐7
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Inverted Index with Location
the dog stood on the mat
the cat stood while a dog sat
the cat sat on the mat
a 3‐5cat 1‐2 3‐2dog 2‐2 3‐6mat 1‐6 2‐6on 1‐4 2‐4sat 1‐3 3‐7stood 2‐3 3‐3the 1‐1 1‐5 2‐1 2‐5 3‐1while 3‐4
1 2 3
query
“cat sat”
1‐2, 3‐2
1‐3, 3‐7
![Page 26: Information Retrieval - cs.brynmawr.edu · Information Retrieval Searching within a document collection for a particular information need. • Traditional vs. web IR • • Query](https://reader034.vdocuments.site/reader034/viewer/2022042402/5f132190fbec4b05971e67b2/html5/thumbnails/26.jpg)
Inverted Index with Location
the dog stood on the mat
the cat stood while a dog sat
the cat sat on the mat
a 3‐5cat 1‐2 3‐2dog 2‐2 3‐6mat 1‐6 2‐6on 1‐4 2‐4sat 1‐3 3‐7stood 2‐3 3‐3the 1‐1 1‐5 2‐1 2‐5 3‐1while 3‐4
1 2 3
query
“cat sat”
1‐2
1‐3
the cat sat on the mat
1
hits
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NEAR* Queries
the dog stood on the mat
the cat stood while a dog sat
the cat sat on the mat
1 2 3
query
cat NEAR dog
the cat stood while a dog sat3
hits
*NEAR: distance <= 5
3‐2
3‐6
a 3‐5cat 1‐2 3‐2dog 2‐2 3‐6mat 1‐6 2‐6on 1‐4 2‐4sat 1‐3 3‐7stood 2‐3 3‐3the 1‐1 1‐5 2‐1 2‐5 3‐1while 3‐4
![Page 28: Information Retrieval - cs.brynmawr.edu · Information Retrieval Searching within a document collection for a particular information need. • Traditional vs. web IR • • Query](https://reader034.vdocuments.site/reader034/viewer/2022042402/5f132190fbec4b05971e67b2/html5/thumbnails/28.jpg)
NEAR* Queries
the dog stood on the mat
the cat stood while a dog sat
the cat sat on the mat
1 2 3
query
cat NEAR dog
the cat stood while a dog sat3
hits
*NEAR: distance <= 5
3‐2
3‐6
a 3‐5cat 1‐2 3‐2dog 2‐2 3‐6mat 1‐6 2‐6on 1‐4 2‐4sat 1‐3 3‐7stood 2‐3 3‐3the 1‐1 1‐5 2‐1 2‐5 3‐1while 3‐4
Useful in ranking!
![Page 29: Information Retrieval - cs.brynmawr.edu · Information Retrieval Searching within a document collection for a particular information need. • Traditional vs. web IR • • Query](https://reader034.vdocuments.site/reader034/viewer/2022042402/5f132190fbec4b05971e67b2/html5/thumbnails/29.jpg)
Matching & Ranking
query
muddy waters
matched pages ranked pages
1.
2.
3.matching ranking
“hits”
![Page 30: Information Retrieval - cs.brynmawr.edu · Information Retrieval Searching within a document collection for a particular information need. • Traditional vs. web IR • • Query](https://reader034.vdocuments.site/reader034/viewer/2022042402/5f132190fbec4b05971e67b2/html5/thumbnails/30.jpg)
Ranking & Relevance
By far the most commoncause of malaria isbeing bitten by aninfected mosquito, butthere are also otherways to contract thedisease.
Our cause was nothelped by the poorhealth of the troops,many of whom weresuffering from malariaand other tropicaldiseases.
1 2
![Page 31: Information Retrieval - cs.brynmawr.edu · Information Retrieval Searching within a document collection for a particular information need. • Traditional vs. web IR • • Query](https://reader034.vdocuments.site/reader034/viewer/2022042402/5f132190fbec4b05971e67b2/html5/thumbnails/31.jpg)
Ranking & Relevance
By far the most commoncause of malaria isbeing bitten by aninfected mosquito, butthere are also otherways to contract thedisease.
Our cause was nothelped by the poorhealth of the troops,many of whom weresuffering from malariaand other tropicaldiseases.
1 2
also 1‐19…cause 1‐6 2‐2…malaria 1‐8 2‐19…whom 2‐15
![Page 32: Information Retrieval - cs.brynmawr.edu · Information Retrieval Searching within a document collection for a particular information need. • Traditional vs. web IR • • Query](https://reader034.vdocuments.site/reader034/viewer/2022042402/5f132190fbec4b05971e67b2/html5/thumbnails/32.jpg)
Ranking & Relevance
By far the most commoncause of malaria isbeing bitten by aninfected mosquito, butthere are also otherways to contract thedisease.
Our cause was nothelped by the poorhealth of the troops,many of whom weresuffering from malariaand other tropicaldiseases.
1 2
also 1‐19…cause 1‐6 2‐2…malaria 1‐8 2‐19…whom 2‐15
query
malaria cause
![Page 33: Information Retrieval - cs.brynmawr.edu · Information Retrieval Searching within a document collection for a particular information need. • Traditional vs. web IR • • Query](https://reader034.vdocuments.site/reader034/viewer/2022042402/5f132190fbec4b05971e67b2/html5/thumbnails/33.jpg)
Ranking & Relevance
By far the most commoncause of malaria isbeing bitten by aninfected mosquito, butthere are also otherways to contract thedisease.
Our cause was nothelped by the poorhealth of the troops,many of whom weresuffering from malariaand other tropicaldiseases.
1 2
also 1‐19…cause 1‐6 2‐2…malaria 1‐8 2‐19…whom 2‐15
query
malaria causeNearness canresolve the ranking!
![Page 34: Information Retrieval - cs.brynmawr.edu · Information Retrieval Searching within a document collection for a particular information need. • Traditional vs. web IR • • Query](https://reader034.vdocuments.site/reader034/viewer/2022042402/5f132190fbec4b05971e67b2/html5/thumbnails/34.jpg)
Using Metadata
![Page 35: Information Retrieval - cs.brynmawr.edu · Information Retrieval Searching within a document collection for a particular information need. • Traditional vs. web IR • • Query](https://reader034.vdocuments.site/reader034/viewer/2022042402/5f132190fbec4b05971e67b2/html5/thumbnails/35.jpg)
Using Metadata<!DOCTYPE HTML PUBLIC "‐//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <html><head><meta http‐equiv="Content‐Type" content="text/html; charset=iso‐8859‐1"> <title>CS380: Science of Information (Course Page)</title></head><body><P><CENTER><h3>Bryn Mawr College<BR CLEAR="ALL"> <B><FONT SIZE="+2">CS 380: Recent Advances in Computer Science<br>Topic: Science of Information</FONT></B><BR CLEAR="ALL"><B><FONT SIZE="+2">Fall 2012</FONT></B><br>BMC Class Number: 1214<BR CLEAR="ALL"><B><FONT SIZE="+2">Course Materials</FONT></B></h3></CENTER>…
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Metadata
my dogthe dog stood on the mat
my petsthe cat stood while a dog sat
my catthe cat sat on the mat
1 2 3
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Metadata
my dogthe dog stood on the mat
my petsthe cat stood while a dog sat
my catthe cat sat on the mat
1 2 3
<title>my dog </title><body>the dog stood on the mat</body>
<title>my pets </title><body>the cat stood while a dog sat
<title>my cat </title> <body>the cat sat on the mat </body>
1 2 3
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Metadata
<title>my dog </title><body>the dog stood on the mat</body>
<title>my pets </title><body>the cat stood while a dog sat
<title>my cat </title> <body>the cat sat on the mat </body>
1
2
3
a 3‐10cat 1‐3 1‐7 3‐7dog 2‐3 2‐7 3‐11mat 1‐11 2‐11my 1‐2 2‐2 3‐2on 1‐9 2‐9pets 3‐3sat 1‐8 3‐12stood 2‐8 3‐8the 1‐6 1‐10 2‐6 2‐10 3‐6while 3‐9<body> 1‐5 2‐5 3‐5</body> 1‐12 2‐12 3‐13<title> 1‐1 2‐1 3‐1</title> 1‐4 2‐4 3‐4
![Page 39: Information Retrieval - cs.brynmawr.edu · Information Retrieval Searching within a document collection for a particular information need. • Traditional vs. web IR • • Query](https://reader034.vdocuments.site/reader034/viewer/2022042402/5f132190fbec4b05971e67b2/html5/thumbnails/39.jpg)
Structure Queriesa 3‐10cat 1‐3 1‐7 3‐7dog 2‐3 2‐7 3‐11mat 1‐11 2‐11my 1‐2 2‐2 3‐2on 1‐9 2‐9pets 3‐3sat 1‐8 3‐12stood 2‐8 3‐8the 1‐6 1‐10 2‐6 2‐10 3‐6while 3‐9<body> 1‐5 2‐5 3‐5</body> 1‐12 2‐12 3‐13<title> 1‐1 2‐1 3‐1</title> 1‐4 2‐4 3‐4
query
intitle: dog
![Page 40: Information Retrieval - cs.brynmawr.edu · Information Retrieval Searching within a document collection for a particular information need. • Traditional vs. web IR • • Query](https://reader034.vdocuments.site/reader034/viewer/2022042402/5f132190fbec4b05971e67b2/html5/thumbnails/40.jpg)
Structure Queriesa 3‐10cat 1‐3 1‐7 3‐7dog 2‐3 2‐7 3‐11mat 1‐11 2‐11my 1‐2 2‐2 3‐2on 1‐9 2‐9pets 3‐3sat 1‐8 3‐12stood 2‐8 3‐8the 1‐6 1‐10 2‐6 2‐10 3‐6while 3‐9<body> 1‐5 2‐5 3‐5</body> 1‐12 2‐12 3‐13<title> 1‐1 2‐1 3‐1</title> 1‐4 2‐4 3‐4
query
intitle: dog
![Page 41: Information Retrieval - cs.brynmawr.edu · Information Retrieval Searching within a document collection for a particular information need. • Traditional vs. web IR • • Query](https://reader034.vdocuments.site/reader034/viewer/2022042402/5f132190fbec4b05971e67b2/html5/thumbnails/41.jpg)
Structure Queriesa 3‐10cat 1‐3 1‐7 3‐7dog 2‐3 2‐7 3‐11mat 1‐11 2‐11my 1‐2 2‐2 3‐2on 1‐9 2‐9pets 3‐3sat 1‐8 3‐12stood 2‐8 3‐8the 1‐6 1‐10 2‐6 2‐10 3‐6while 3‐9<body> 1‐5 2‐5 3‐5</body> 1‐12 2‐12 3‐13<title> 1‐1 2‐1 3‐1</title> 1‐4 2‐4 3‐4
query
intitle: dog
![Page 42: Information Retrieval - cs.brynmawr.edu · Information Retrieval Searching within a document collection for a particular information need. • Traditional vs. web IR • • Query](https://reader034.vdocuments.site/reader034/viewer/2022042402/5f132190fbec4b05971e67b2/html5/thumbnails/42.jpg)
Structure Queriesa 3‐10cat 1‐3 1‐7 3‐7dog 2‐3 2‐7 3‐11mat 1‐11 2‐11my 1‐2 2‐2 3‐2on 1‐9 2‐9pets 3‐3sat 1‐8 3‐12stood 2‐8 3‐8the 1‐6 1‐10 2‐6 2‐10 3‐6while 3‐9<body> 1‐5 2‐5 3‐5</body> 1‐12 2‐12 3‐13<title> 1‐1 2‐1 3‐1</title> 1‐4 2‐4 3‐4
query
intitle: dog
![Page 43: Information Retrieval - cs.brynmawr.edu · Information Retrieval Searching within a document collection for a particular information need. • Traditional vs. web IR • • Query](https://reader034.vdocuments.site/reader034/viewer/2022042402/5f132190fbec4b05971e67b2/html5/thumbnails/43.jpg)
Structure Queriesa 3‐10cat 1‐3 1‐7 3‐7dog 2‐3 2‐7 3‐11mat 1‐11 2‐11my 1‐2 2‐2 3‐2on 1‐9 2‐9pets 3‐3sat 1‐8 3‐12stood 2‐8 3‐8the 1‐6 1‐10 2‐6 2‐10 3‐6while 3‐9<body> 1‐5 2‐5 3‐5</body> 1‐12 2‐12 3‐13<title> 1‐1 2‐1 3‐1</title> 1‐4 2‐4 3‐4
query
intitle: dog
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Structure Queriesa 3‐10cat 1‐3 1‐7 3‐7dog 2‐3 2‐7 3‐11mat 1‐11 2‐11my 1‐2 2‐2 3‐2on 1‐9 2‐9pets 3‐3sat 1‐8 3‐12stood 2‐8 3‐8the 1‐6 1‐10 2‐6 2‐10 3‐6while 3‐9<body> 1‐5 2‐5 3‐5</body> 1‐12 2‐12 3‐13<title> 1‐1 2‐1 3‐1</title> 1‐4 2‐4 3‐4
query
intitle: dog
<title>my dog </title><body>the dog stood on the mat</body>
2
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Web Information Retrieval
• Search Engines• Queriesphrase queriesstructure queries (NEAR, intitle:, …)
• Matching• Inverted Indexpage numberlocation
• Ranking & Relevance• Metadata
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Web Information Retrieval
• Search Engines• Queriesphrase queriesstructure queries
• Matching• Inverted Indexpage numberlocation
• Ranking & Relevance• Metadata
Efficient matchingis only one half the story.
The other grand challengeis how to rank the matching pages
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References
• Google’s PageRank and Beyond, Amy N. Langville and Carl D. Meyer, Princeton University Press, 2006.
• Nine Algorithms That Changed The Future, John MacCormick, Princeton University Press, 2012.
• Learning Computing with Robots, Deepak Kumar, IPRE 2011.