CPS 49S Google: The Computer Science Within and its Impact on Society Shivnath Babu Spring 2007

Discussion Format Talk for minutes –Give an overview Give an outline the discussion points that you have come up with Need a scribe –Volunteer?

Note Make it a habit to check the course web page daily for: –Updated notes (presentation, discussion report, and scribe notes) –Current and future schedule –Announcements

Introduction Let us look at some numbers –From the paper –From searchenginewatch.com

Introduction (contd.) Terms –HTML (look at the HTML for the class web page), Hypertext, link/hyperlink, inlink, outlink, anchor text, link graph –Search engine, meta search engine –Information retrieval, crawl, index Terms that we will discuss later –PageRank, proximity, barrel, …

Discussion Points Motivation for Google –Human-maintained lists –Keyword matching only –Advertising --- conflict of interest

Discussion Points Design Goal #1: High-quality search results –Hypertext –Proximity –PageRank Design Goal #2: Good performance Design Goal #3: Support for research activities

Next Problem: User types in a keyword-based search query. We have to (i) find result pages to answer this query, and (ii) rank these result pages –Proximity of terms –Anchor text –PageRank

Proximity Of terms on a web page E.g., phrases E.g., “anatomy”, “search”, “anatomy search” E.g., “google freshman seminar duke” Other examples?

Anchor text Text around the link Often accurate and concise description of page May have terms that the page does not contain –“search engine” –Other examples? Can return pages that have not been crawled

PageRank First cut: count inlinks Basic idea --- “recursive” counting Interpretation based on probability Demo

Assigned Readings For Tue (1/23) –Continuation of the anatomy paper –Paper on “Taxonomy of Web Search”