Searching the Web

1
Searching the Web

• Using Search Engines and Directories Effectively

2
Types of Search Questions

• Specific Question can be phrased easily
  answer is readily recognizable
  
• Exploratory Question open-ended question, can
  be difficult to phrase, can be difficult to
  determine when a good answer is found

3
Web Search Strategy

• Four Steps
• Carefully formulate and state question
• Select appropriate search tools to use
• Evaluate results
• Refine/redefine question and maybe use different
  search tool

4
Web Search Tools

• Search engines
• Directories
• Metasearch engines
• Other Web resources (e.g. Web bibliographies)

5
Search Engines (1)

• Definition a Web site that finds other Web
  pages that match a word or phrase (search
  expression or query)
  
• Hit a Web page that is indexed in a search
  engines database and contains text that matches
  your query
  
• Results pages Web pages containing hyperlinks
  to other Web pages that contain text that match
  your query
  

6
Search Engines (2)

• A search engine does not search the Web to find a
  match but searches its own database of
  information about Web pages it has collected,
  indexed, and stored
• Database is built using Web robots and Web page
  submissions
  

7
Search Engines (3)

• Search engines generate revenue from
• sponsored links and banner ads
• Sponsored links links that appear because of
  payments by an advertiser
  
• Banner Ads advertising that appears on a Web
  page (top, side, or bottom)
  

8
Search Engines (4)

• Why do search engines give different results?
  Each
  
• search engine
• Uses a different Web robot to gather information
  about Web pages
  
• Stores a different amount of Web page text in its
  database
  
• Selects different Web pages to index
• Has different storage resources
• Interprets queries somewhat differently
• Read Help pages on each search engine site to
  understand how queries are interpreted
  

9
Search Engines (5)

• Meta tag HTML code a Web page creator places in
  a Web page header to inform Web robots about the
  pages contents
  
• Page ranking way of grading Web pages by number
  of other Web pages that link to them (highest
  appear first on search results page)
  
• Natural language query interface users can
  enter a question exactly as they would normally
  ask it
  

10
Directories (1)

• Web directory a listing of hyperlinks to Web
  pages organized into hierarchical categories
  
• Web pages in directory are selected and organized
  into categories before visitors use the
  directory
  
• Most Web directories have human editors who
  decide which Web pages will be included and how
  they will be organized
  
• Main weakness user must know which category most
  likely contains the information they want

11
Directories (2)

• Hybrid search engine directory combination of
  search engine web directory (most web
  directories today have this capability)
  
• Open Directory Project Web directory where
  editors volunteer their time create the
  directorys entries

12
Metasearch Engines

• Definition a tool that combines the power of
• multiple search engines
• Do not have their own databases of Web
  information
  
• Accept queries and transmit them to several
  search engines
  
• Each search engine runs the queries and returns
  results to metasearch engine
  
• Metasearch engine then reports consolidated
  results from all search engines it queried

13
Other Web Resources (1)

• Web bibliographies a Web site that contains a
• list of hyperlinks to other Web pages that
• contain information about a particular topic or
• group of topics and often includes summaries
• or reviews of the Web pages listed
• Also called resource lists subject guides
  clearinghouses virtual libraries
  

14
Other Web Resources (2)

• Similar to bibliographies but instead of listing
  books and journal articles, contain lists of
  hyperlinks to Web pages
  
• More focused on specific subjects than Web
  directories usually do not include a search
  tool for searching within their categories
  
• Many are created by librarians at university and
  public libraries
  
• Find Web bibliographies on specific subjects by
  adding subject guide to the end of a query

15
Complex Searches

• Require more complex queries or use of a
• search engines advanced querying page
• Boolean logic (logical operators) specify the
  logical relationship between elements they join
  (AND, OR, NOT) and are recognized by many search
  engines
• Precedence (grouping) operators clarify
  grouping within a complex query (using
  parentheses symbols)
  
• Wildcard characters allow you to omit part of a
  search term, usually an asterisk ()
  
• Search filters many search engines allow you to
  restrict your search by using search filters

16
Search Engines with Clustering Features

• Vivisimo a search engine that uses an
• advanced technology to group its results
• into clusters
• Provides results that are easier to review,
  rather than scrolling through hundreds of results
  pages looking for useful links

17
Future of Web Search Tools

• Current search engines have a weakness they
  only search Static Web pages (HTML files that
  exist on a Web server computer)
  
• Increasing number of Web sites store information,
  not as HTML files, but in databases which
  cannot be found or examined by search engine
  robots
• When users submits queries, the Web server
  searchers the database and generates a Web page
  called Dynamic Web pages
  
• This information is called the deep Web hidden
  Web invisible Web

18
Evaluating the Validity and Quality of Web
Resources (1)

• The Web has made publishing easy and inexpensive,
  however this information is seldom subjected to
  review and editing
  
• So there is risk in relying on Web information
• Such risks can be reduced by carefully evaluating
  the quality of any Web resources

19
Evaluating the Validity and Quality of Web
Resources (2)

• How can you evaluate the validity and
• quality of a Web page?
• Author identity and objectivity determine
  author, qualifications, independence,
  objectivity
  
• Content timeliness, relevancy,
  comprehensiveness
  
• Form and Appearance quality of Web site itself