Presentation is loading. Please wait.

Presentation is loading. Please wait.

Some Popular Portals Yahoo! :

Similar presentations

Presentation on theme: "Some Popular Portals Yahoo! :"— Presentation transcript:

1 Some Popular Portals Yahoo! :
Portals to the World from the Library of Congress: AltaVista:




5 Search Engines? A search engine is a web site that uses software to browse the Internet. A search engine will retrieve a listing of World Wide Web sites related to the key words you specify.

6 How Search Engines Work
Read pages they find on the web (spider) Store text in an “index” When you search, they look for pages with matching text Other factors involved in “ranking” those pages, such as “link popularity”

7 Search Engine INdexing
Computer-driven search tool Website owners submit web address of their homepage for inclusion in the database Robots periodically spider the Web, detect the homepage and proceed to scan every page in the entire website (The first words on the homepage appear as the ‘result’ the user sees in the search engine)

8 Search Engines Crawler-based Search Engines Human-based Search Engines
“Spiders” or “Crawlers” visit websites and some of their pages periodically, and adds to index Scans links and adds them to their index Returns the information to the index or catalog Search engine software sifts the index and ranks in relevant order Human-based Search Engines Mixed Focused Crawlers: LawCrawler ( Part of the Fedlaw service which also has a targeted directory. sponsored by the APA

9 Directories Vs Search Engines
When should you use a directory? When you have a broad topic When you want experts to recommend sites When you want to avoid irrelevant sites Examples topics: Disabilities Civil War Welfare

10 Directories Vs Search Engines
When should you use a search engine? When you have a narrow topic When you are looking for a specific website When you want to search for a file type or language Examples: Americans with Disabilities Act Battle of Gettsyburg Welfare to Work

11 Start Your Search Engines Here
Google AllTheWeb Yahoo MSN Why? See:

12 Other Search Engine Types
News Search Engines Multimedia Search Engines Metacrawlers Kids Search Engines Regional Search Engines Scientific Search Engines

13 Top Search Engines & Directories
Google Yahoo! AllTheWeb AltaVista Open Directory MSN Search About Ask Jeeves WiseNut HotBot LookSmart Teoma AOL Search iLOR

14 Google Google is the undisputed leader in search engines, with the largest database and highly relevant results Uses an algorithm based on site popularity The more inbound links pointing to a particular site from another site Google thinks is worthwhile, then that site will receive a higher page rank in the results Wary of minimising advertising - no frills design, nice clean look and no pop-up ads

15 AllTheWeb & AltaVista AllTheWeb used to be a Norwegian search engine FAST and for a while was one of the Web’s best kept secrets AltaVista was the first search engine in 1995 and was THE search engine before Google existed Recently, Overture acquired FAST and AltaVista This year, Yahoo! acquired Overture and Inktomi, making Yahoo! the largest network of major search tools on the Internet AllTheWeb & AltaVista’s future are now unknown, as many results are simply retrieved from Yahoo

16 Open Directory & Ask Jeeves
Open Directory Project is the largest humanly-compiled search directory on the Web As each website is considered for inclusion by a human (many don’t make it) - quality is assured Ask Jeeves uses special natural language technology, so the user can ask a complete question instead of inputting only a few words It then searches its own database and supplements this with results from Teoma Ask Jeeves is popular with young Web users

17 Understand Limitations of Search Engines
Search “spiders” or “crawlers” do *not* crawl in real time Lag times getting info to the index vary by search engine If a website is not submitted to the search engine it won’t be crawled Not every page from a website is crawled A webmaster can choose to not have a page crawled Formats like PDF, Flash, Zip files, executable programs, and others cannot be searched The “Invisible Web” If a webpage has no links pointing to it from another page the crawler can’t find it.

18 Evaluating Web Sites Continued…
Can you find this news reported on a legitimate news website? Who is the sponsor of the website? Are there inconsistencies or inaccuracies in the information? If an organization is mentioned by name, does the organization have any related information on this website?

19 Meta Search Engine Searches more than one search engine simultaneously (often up to fifteen) Each meta search engine normally searches a different combination of search engines Simultaneous multiple engine searching saves the user lots of time But meta search engines only skim the surface of each engine’s database and sometimes lack depth when searching for results

20 Top Meta Search Engines
Kartoo Turbo 10 Dogpile Mamma Red Hot Chilli Meta Eureka Web Taxi Vivisimo ixquick iBoogie Metacrawler Supercrawler Query Server

21 Kartoo & Turbo10 These search tools cluster sets of results on similar topics and display them on the side frame Kartoo is arguably the funkiest search facility on the Web, displaying results as a visual mind map There’s a basic and expert version for searching Turbo10 is unique because it has a long list of specialist databases on specific subjects Searches the Deep Net (others rarely go there) Users can also tailor their searching by selecting unusual databases of their own choosing

22 Vivisimo, Dogpile & Mamma
Vivisimo also uses clustering technology and allows users to choose their own search engines Dogpile was one of the earliest meta search engines and remains very popular today It’s major advantage lies in its search engines: Google, Yahoo!, Ask Jeeves, Teoma, About etc. Canadian-based Mamma began in 1996 as a Masters thesis, arguably the first meta search Today it is a well respected search tool and like Dogpile, searches the Web’s top engines such as Google, Open Directory, Teoma and others

23 Image ( + Meta) Searching
Although pictures on websites often appear neatly embedded amongst text, each image needs a unique URL, allowing picture searching Google’s image search is one of the best on the Web, partly because of the size of its database There are also excellent picture meta search engines: iBoogie, Dogpile, ixquick and 1Banana picsearch is solely a picture search engine and markets itself as family and user friendly

24 Language Translation Google and AltaVista offer language translation
Google will allow you to translate a foreign language website or page and even allow you to link to the translated page from another website AltaVista uses Babel Fish for its translation and you can also translate blocks of text Some of the best websites on Bertolt Brecht and his Epic Theatre are actually in German, so this is an example of where translation tools are worthwhile if you speak another language

25 Useful Reference Tools
You can find free dictionaries online, such as Merriam Webster, Oxford, Macquarie, Cambridge and Most dictionaries also have a thesaurus tab The meta dictionary OneLook simultaneously searches nearly 1,000 generalist and specialist dictionaries! Some of the weirdest words out there are at the Strange and Unusual Dictionaries website Or visit RyhmeZone’s Rhyming Dictionary & Thesaurus for a bit of fun!

26 More Reference Tools If looking for the origin of a phrase or saying, try Brewer’s Dictionary of Phrase and Fable There’s also the ClichéSite or the Hutchinson Dictionary of Difficult Words Free encyclopaedias include, Columbia, Encarta (partly free), Wikipedia, Hutchinson & the 1911 Encyclopaedia Britannica considered by many to be the best edition ever! Way Back Machine has been archiving large portions of the Web since 1996, so if a website has suddenly disappeared, search for it here!

27 The Invisible Web Web information that does not get indexed by the major search engines. Hidden mostly in databases or have robot.txt file attached Data created on the fly from the backend (cgi-bin, etc) More than ¾ of information on the Web is part of the IW.

28 The Invisible Web – 4 Types
Opaque: search engines choose not to index The Private Web: password protected The Proprietary Web: registration required (either fee or free) The Truly Invisible Web: can’t search certain file formats and databases OPAQUE: Depth of crawl is limited – sometimes for cost reasons Frequency of crawl is limited - pages that change every day are affected Maximum Number of Results PRIVATE: password protected, robots files disallows spiders access, “noindex” meta tag prevents access PROPRIETARY: either free or fee registration is required. Examples are The New York Times, The Well, The Wall Street Journal Interactive Edition. TRULY INVISIBLE: file formats like PDF, Flash, Shockwave, etc.; dynamically generated web pages

29 Examples of the IW Online telephone and address databases News engines
Professional look-up services (AMA) Movie and Book Reviews Education databases (ERIC) Medical databases (Medline)

Download ppt "Some Popular Portals Yahoo! :"

Similar presentations

Ads by Google