Chapter 6 : Different Types of Search Engines

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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.

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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.

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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
  engines sponsored results list.
• The sponsored list should be separated from the
  organic list.
• PPC is a major revenue source for search engines.

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Paid Placement

• Figure 6.1 Query chess submitted to Overture

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MetaSearch

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

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Clustering Search Results

• Figure 6.4 Query chess submitted to Clusty

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Personalised Results Tool

• Figure 6.5 PResTo! for query salsa

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Relevance Feedback

• Technique originally developed by Rocchio in the
  1960s. 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.

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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.

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Question Answering (QA) on the Web

• Ask Jeeves originally a QA service, which has
  evolved into a fully fledged search engine.
• QA is moving away from being annotation-based to
  using humanly compiled databases and the open web
  as information sources.

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Question Answering

• Figure 6.7 Google answer to question
• who is the prime minister of the uk?

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Question Answering

• Figure 6.8 MSN Search answer to question
• who is the prime minister of the uk?

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Image Search

• Figure 6.9 Google images for chess

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Image Search

• Figure 6.10 Yahoo! images for chess

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Image Search

• Figure 6.11 Picsearch images for chess

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Special Purpose Search Engines

• Amazon.com for finding books.
• News search engines.
• CiteSeer scientific digital library.
• Kids search engines.
• Wikipedia collaboratively edited free
  encyclopaedia.