advantages
- The indexes of search engines are usually vast, representing significant portions of the Internet, offering a wide variety and quantity of information resources.
- The growing sophistication of search engine software enables us to precisely describe the information that we seek.
- The large number and variety of search engines enriches the Internet, making it at least appear to be organized.
- Regardless of the growing sophistication, many well thought-out search phrases produce list after list of irrelevant web pages. The typical search still requires sifting through dirt to find the gems.
- Using search engines does involve a learning curve. Many beginning Internet users, because of these disadvantages, become discouraged and frustrated.
- A Search Engine has 3 Basic Parts1. Spider (crawler, link finder): a computer program that harvests web links from page to page2. Index: a database that is organized and searchable of the Spider's harvested results3. Search and retrieval mechanism: Software that allows users to search the Index and return results in a predetermined order.But a Search Engine also is commonly used to refer to any software that searches an Index of Words or material types
- A meta-search engine is a search tool that sends user requests to several other search engines and/or databases and aggregates the results into a single list or displays them according to their source. Meta search engines enable users to enter search criteria once and access several search engines simultaneously.
3.When is it appropriate to use a search engine?
- when you are trying to search for the specific words or topic.
4.When is it appropriate to use a search/subject directory?
- when you are trying to search just from general and to specific like searching for concepts or subject categories.
5.What is an invisible web or 'Deep Web'?
- The "invisible web" is what you cannot find using these types of tools.
- The terms invisible web, hidden web, and deep web all refer to the same thing: a massive storehouse of online data that the search engines don't capture. That's because terabytes of information are buried in databases and other research resources. Searchable and accessible online but often ignored by conventional search engines, these resources exist by the thousands. Known in research circles as the invisible, deep, or hidden Web, this buried content is an estimated 500 times larger than the surface Web, which is estimated at over four billion pages. This mass of information represents a potent research resource, no matter what your discipline or interest.
6.How do you find an invisible web?
The term "invisible web" mainly refers to the vast repository of information that search engines and directories don't have direct access to, like databases.
Simply think "databases" and keep your eyes open. You can find searchable databases containing invisible web pages in the course of routine searching in most general web directories. Of particular value in academic research are:
Use Google and other search engines to locate searchable databases by searching a subject term and the word "database". If the database uses the word database in its own pages, you are likely to find it in Google. The word "database" is also useful in searching a topic in the Google Directory or the Yahoo! directory, because they sometimes use the term to describe searchable databases in their listings.
- Examples:
- plane crash database
- languages database
- toxic chemicals database
7.Why are these web pages not available in search engines or object directories?
The data is there only for a short lifetime, and then disappears forever having been received, displayed and discarded just as easily. Only a very minimal amount of specific information is associated with these events, so there is no URL for general access -- meaning the information cannot be captured and searched on the web
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