Mark Levene, An Introduction to Search Engines and Web Navigation © Pearson Education Limited 2005 Slide 6.1 Chapter 6 : Different Types of Search Engines Web directories. Paid Inclusion and Paid Placement. Metasearch. Clustering search results. Personalising search results. Question answering. Image search. Special purpose search engines.

Mark Levene, An Introduction to Search Engines and Web Navigation © Pearson Education Limited 2005 Slide 6.2 Directories and Categorisation of Web Content Important alternative, esp. for novice surfers. Yahoo! Open Directory Looksmart Decision of whether to include a page in the directory is made by human editors.

Mark Levene, An Introduction to Search Engines and Web Navigation © Pearson Education Limited 2005 Slide 6.3 Paid Inclusion and Paid Placement Paid inclusion – payment to speed up inclusion in the search index. Pay-Per-Click (PPC) or Cost-Per-Click (CPC) – payment for being advertised on the search engine’s sponsored results list. The sponsored list should be separated from the organic list. PPC is a major revenue source for search engines.

Mark Levene, An Introduction to Search Engines and Web Navigation © Pearson Education Limited 2005 Slide 6.4 Paid Placement Figure 6.1 : Query “chess” submitted to Overture

Mark Levene, An Introduction to Search Engines and Web Navigation © Pearson Education Limited 2005 Slide 6.5 MetaSearch Combine result lists from several search engines. (No search index or crawler needed.) Operational metasearch engines include: –DogpileDogpile –MetacrawlerMetacrawler –SavvySearchSavvySearch –ProFusionProFusion –ClustyClusty

Mark Levene, An Introduction to Search Engines and Web Navigation © Pearson Education Limited 2005 Slide 6.6 Clustering Search Results Figure 6.4 : Query “chess” submitted to Clusty

Mark Levene, An Introduction to Search Engines and Web Navigation © Pearson Education Limited 2005 Slide 6.7 Personalised Results Tool Figure 6.5: PResTo! for query “salsa”

Mark Levene, An Introduction to Search Engines and Web Navigation © Pearson Education Limited 2005 Slide 6.8 Relevance Feedback Technique originally developed by Rocchio in the 1960’s. The idea is as follows: –User marks documents in the result list as being either relevant or non-relevant. –Weights of keywords in relevant docs are increased, and in non-relevant docs are decreased. –Query is reformulated and resubmitted to search engine. –The process can be iterated until the user is satisfied or the results do not change.

Mark Levene, An Introduction to Search Engines and Web Navigation © Pearson Education Limited 2005 Slide 6.9 Personalised PageRank Change T/N with Tv Instead of teleporting uniformly to any page we bias the jump to prefer some pages over others. –E.g. v has 1 for your home page and 0 otherwise. –E.g. v prefers the topics you are interested in.

Mark Levene, An Introduction to Search Engines and Web Navigation © Pearson Education Limited 2005 Slide 6.10 Question Answering (Q&A) on the Web Ask Jeeves – originally a Q&A service, which has evolved into a fully fledged search engine.Ask Jeeves Q&A is moving away from being annotation- based to using humanly compiled databases and the open web as information sources.

Mark Levene, An Introduction to Search Engines and Web Navigation © Pearson Education Limited 2005 Slide 6.11 Question Answering Figure 6.7: Google answer to question “who is the prime minister of the uk?”

Mark Levene, An Introduction to Search Engines and Web Navigation © Pearson Education Limited 2005 Slide 6.12 Question Answering Figure 6.8: MSN Search answer to question “who is the prime minister of the uk?”

Mark Levene, An Introduction to Search Engines and Web Navigation © Pearson Education Limited 2005 Slide 6.13 Image Search Figure 6.9: Google images for “chess”

Mark Levene, An Introduction to Search Engines and Web Navigation © Pearson Education Limited 2005 Slide 6.14 Image Search Figure 6.10: Yahoo! images for “chess”

Mark Levene, An Introduction to Search Engines and Web Navigation © Pearson Education Limited 2005 Slide 6.15 Image Search Figure 6.11: Picsearch images for “chess”

Mark Levene, An Introduction to Search Engines and Web Navigation © Pearson Education Limited 2005 Slide 6.16 Special Purpose Search Engines Amazon.com for finding books.Amazon.com News search engines. CiteSeer – scientific digital library.CiteSeer Kids search engines. Wikipedia – collaboratively edited free encyclopaedia.Wikipedia …