webmining overview
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CS 345AData MiningLecture 1
Introduction to Web Mining
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What is Web Mining?
Discovering useful information from the World-Wide Web and its usage patterns
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Web Mining v. Data Mining
Structure (or lack of it) Textual information and linkage structure
Scale Data generated per day is comparable to
largest conventional data warehouses Speed
Often need to react to evolving usage patterns in real-time (e.g., merchandising)
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Web Mining topics
Web graph analysis Power Laws and The Long Tail Structured data extraction Web advertising Systems Issues
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Web Mining topics
Web graph analysis Power Laws and The Long Tail Structured data extraction Web advertising Systems Issues
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Size of the Web
Number of pages Technically, infinite Much duplication (30-40%) Best estimate of “unique” static HTML
pages comes from search engine claims Google = 8 billion(?), Yahoo = 20 billion
Number of web sites Netcraft survey says 72 million sites
(http://news.netcraft.com/archives/web_server_survey.html)
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Netcraft survey
http://news.netcraft.com/archives/web_server_survey.html
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The web as a graph
Pages = nodes, hyperlinks = edges Ignore content Directed graph
High linkage 8-10 links/page on average Power-law degree distribution
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Structure of Web graph
Let’s take a closer look at structure Broder et al (2000) studied a crawl of
200M pages and other smaller crawls Bow-tie structure
Not a “small world”
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Bow-tie Structure
Source: Broder et al, 2000
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What can the graph tell us?
Distinguish “important” pages from unimportant ones Page rank
Discover communities of related pages Hubs and Authorities
Detect web spam Trust rank
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Web Mining topics
Web graph analysis Power Laws and The Long Tail Structured data extraction Web advertising Systems Issues
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Power-law degree distribution
Source: Broder et al, 2000
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Power-laws galore
Structure In-degrees Out-degrees Number of pages per site
Usage patterns Number of visitors Popularity
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The Long Tail
Source: Chris Anderson (2004)
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The Long Tail
Shelf space is a scarce commodity for traditional retailers Also: TV networks, movie theaters,…
The web enables near-zero-cost dissemination of information about products Action moves from Hits to Niches
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The Long Tail
More choice necessitates better filters Recommendation engines (e.g., Amazon) How Into Thin Air made Touching the
Void a bestseller In fact, page rank can be seen as a
long tail filter Tapping into the Wisdom of Crowds
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Web Mining topics
Web graph analysis Power Laws and The Long Tail Structured data extraction Web advertising Systems Issues
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Extracting Structured Data
http://www.simplyhired.com
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Extracting structured data
http://www.fatlens.com
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Web Mining topics
Web graph analysis Power Laws and The Long Tail Structured data extraction Web advertising Systems Issues
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Searching the Web
Content aggregatorsThe Web Content consumers
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Ads vs. search results
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Ads vs. search results
Search advertising is the revenue model Multi-billion-dollar industry Advertisers pay for clicks on their ads
Interesting problems What ads to show for a search? If I’m an advertiser, which search terms
should I bid on and how much to bid?
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Sidebar: What’s in a name?
Geico sued Google, contending that it owned the trademark “Geico” Thus, ads for the keyword geico couldn’t
be sold to others Court Ruling: search engines can sell
keywords including trademarks No court ruling yet: whether the ad
itself can use the trademarked word(s)
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Web Mining topics
Web graph analysis Power Laws and The Long Tail Structured data extraction Web advertising Systems Issues
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Systems architecture
Memory
Disk
CPU
Machine Learning, Statistics
“Classical” Data Mining
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Very Large-Scale Data Mining
Mem
Disk
CPU
Mem
Disk
CPU
Mem
Disk
CPU…
Cluster of commodity nodes
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Systems Issues
Web data sets can be very large Tens to hundreds of terabytes
Cannot mine on a single server! Need large farms of servers
How to organize hardware/software to mine multi-terabye data sets Without breaking the bank!
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Web Mining topics
Web graph analysis Power Laws and The Long Tail Structured data extraction Web advertising Systems Issues
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Web Mining Project
Lots of interesting project ideas If you can’t think of one please come
discuss with us Data and Infrastructure
Webbase data (older Stanford web crawl) Recent web crawl and server courtesy of
Kosmix
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The World-Wide Web
Our modern-day Library of Alexandria
The Web