Jaya S

META-SEARCH ENGINE

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. Metasearch engines enable users to enter search criteria once and access several search engines simultaneously. Metasearch engines operate on the premise that the Web is too large for any one search engine to index it all and that more comprehensive search results can be obtained by combining the results from several search engines. This also may save the user from having to use multiple search engines separately.

A meta search engine searches multiple search engines from a single search page.

Meta search engines work in various ways. With some, a single, simultaneous search retrieves results from multiple sources, usually with the duplicates removed. Others offer a separate search of multiple content sources, allowing you to select the source(s) you want for each search.

When a single simultanous search is offered, only a limited maximum muber of pages from each source are returned. The cut-off may be determined by the number of pages retrieved, or by the amount of time the meta engine spends at the other sites. Results retrieved by these engines can be highly relevant, since they are usually grabbing the first items from the relevancy-ranked list of results returned by the individual search engines. Keep in mind that complex searches, such as field searches, are usually not available.

Operation:

Metasearch engines create what is known as a virtual database. They do not compile a physical database or catalogue of the web. Instead, they take a user's request, pass it to several other heterogeneous databases and then compile the results in a homogeneous manner based on a specific algorithm.

Definition of Meta Search Engine:

A meta search engine (also known as a multi-threaded engine) is a search tool that sends your query simultaneously to several search engines (SEs), Web directories (WDs) and sometimes to the so-called Invisible (Deep) Web, a collection of online information not indexed by traditional search engines. After collecting the results, the meta search engine (MSE) will remove the duplicate links and, according to its algorithm, combine/rank the results into a single merged list.

An important note:

Unlike the individual search engines and directories, the meta search engines:
1. Do not have their own databases and
2. Do not accept URL submissions.

Pros and Cons of Meta Search Engines:

Pros: MSEs save searchers a considerable amount of time by sparing them the trouble of running a query in each search engine. The results - most of the time - are extremely relevant.

Cons: Because some SEs or WDs do not support advanced searching techniques such as quotation marks to enclose phrases or Boolean operators, no (or irrelevant) results from those SEs will appear in the MSEs results list when those techniques are used.

When to use a meta search engine?

* When you want to retrieve a relatively small number of relevant results

* When your topic is obscure

* When you are not having luck finding what you want

* When you want the convenience of searching a variety of different content sources from one search page

Examples of meta search engines:

* Browsys

* Dogpile