WHAT ARE SEARCH ENGINES?
Search engines are huge databases of web page files that have been assembled automatically by machine. Search engines are websites that are designed to find other websites.
There are two types of search engines:
Search engines are huge databases of web page files that have been assembled automatically by machine. Search engines are websites that are designed to find other websites.
There are two types of search engines:
- Individual. Individual search engines compile their own searchable databases on the web.
- Meta. Metasearchers do not compile databases. Instead, they search the databases of multiple sets of individual engines simultaneously (at the same time).
HOW DO SEARCH ENGINES WORK?
Search engines compile their databases by employing "spiders" or "robots" ("bots") to crawl through web space from link to link, identifying and following pages. Sites with no links to other pages may be missed by spiders altogether. Once the spiders get to a web site, they typically index most of the words on the publicly available pages at the site.
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Whenever you search the web using a search engine, you're asking the engine to scan its index of sites and match your keywords and phrases with those in the texts of documents within the engine's database.
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If the embedded clip does not play, try this site: How Search Works. If all else fails, ask your teacher to play it for you.
It is important to remember that when you are using a search engine, you are NOT searching the entire web as it exists at this moment. You are actually searching a portion of the web, captured in a fixed index created, at an earlier date. How much earlier? It's hard to say. Spiders regularly return to the web pages they index to look for changes. When changes occur, the index is updated to reflect the new information. However, the process of updating can take a while, depending upon how often the spiders make their rounds and then, how promptly the information they gather is added to the index. Until a page has been both "spidered" AND "indexed," you won't be able to access the new information. NOTE: While most search engine indexes are not "up to the minute" current, they have tried to become more current by linking with specialised news databases because they are current. For breaking news, look for a "news" tab somewhere on the search engine or directory page. Examples include: WHAT ARE THE PROS AND CONS OF SEARCH ENGINES? PROS: Search engines provide access to a fairly large portion of the publicly available pages on the Web, which itself is growing exponentially. (see "How Big Is the Internet 1?" and/or "How Big Is the Internet 2?") |
CONS:
On the down side, the sheer number of words indexed by search engines increases the likelihood that they will return hundreds of thousands of responses to simple search requests. Remember, they will return lengthy documents in which your keyword appears only once. Many of these responses will be irrelevant to your search. ARE SEARCH ENGINES ALL THE SAME? Although search engine software programs may be similar, no two search engines are exactly the same in terms of size, speed and content; no two search engines use exactly the same ranking schemes, and not every search engine offers you exactly the same search options. Therefore, your search is going to be different on every engine you use. The difference may not be a lot, but it could be significant. Recent estimates* put search engine overlap at approximately 12% and unique content at around 88%. HOW DO SEARCH ENGINES RANK WEB PAGES?When ranking web pages, search engines follow a set of rules that vary from one engine to another. Their goal is to return the most relevant pages at the top of their lists. To do this, they look for the location and frequency of keywords and phrases in the web page document and, sometimes, in the HTML META tags. Some of them assess popularity by the number of links that are pointing to sites; the more links, the greater the popularity, i.e., value of the page.
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Activity Time 1
Choose two search engines from Kids search engines or General search engines on the Symbaloo page below. Search for "Volcanoes". You will be comparing the use, look and results that the search engines give you.
Download the Compare and Contrast table and save it in your class folder.
Limits:
Up to 2 pages of results in each search engine
Keep the compare contrast table to 1 page
Consider:
Comparisons like:
Same websites…… different websites…. Videos….pictures…. Relevancy… too hard… too easy…reliability of information..
Download the Compare and Contrast table and save it in your class folder.
Limits:
Up to 2 pages of results in each search engine
Keep the compare contrast table to 1 page
Consider:
Comparisons like:
Same websites…… different websites…. Videos….pictures…. Relevancy… too hard… too easy…reliability of information..
s3_compare-contrast.doc | |
File Size: | 36 kb |
File Type: | doc |
Search Engines
Grouping Key: White = Kids search engines; Yellow = metadata search engines; Orange = General search engines; Red = Visual-relational search engines; Purple = Subject search engines; Pink = Australian search engines; Black = Dictionaries with a difference; Teal = Search help