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Chapter 6 : Different Types of Search Engines

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. Directories and Categorisation of Web Content.

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Chapter 6 : Different Types of Search Engines

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  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.

  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.

  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.

  4. Paid Placement Figure 6.1 : Query “chess” submitted to Overture

  5. MetaSearch • Combine result lists from several search engines. (No search index or crawler needed.) • Operational metasearch engines include: • Dogpile • Metacrawler • SavvySearch • ProFusion • Clusty

  6. Clustering Search Results Figure 6.4 : Query “chess” submitted to Clusty

  7. Personalised Results Tool Figure 6.5: PResTo! for query “salsa”

  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.

  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.

  10. Question Answering (Q&A) on the Web • Ask Jeeves – originally a Q&A service, which has evolved into a fully fledged search engine. • Q&A is moving away from being annotation-based to using humanly compiled databases and the open web as information sources.

  11. Question Answering Figure 6.7: Google answer to question “who is the prime minister of the uk?”

  12. Question Answering Figure 6.8: MSN Search answer to question “who is the prime minister of the uk?”

  13. Image Search Figure 6.9: Google images for “chess”

  14. Image Search Figure 6.10: Yahoo! images for “chess”

  15. Image Search Figure 6.11: Picsearch images for “chess”

  16. Special Purpose Search Engines • Amazon.com for finding books. • News search engines. • CiteSeer – scientific digital library. • Kids search engines. • Wikipedia – collaboratively edited free encyclopaedia. • …

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