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Jul 26, 2010

Search Engine optimization

The Pros and Cons of Meta Search Engines 
By Chuck Paulson
Published 05/7/2009

The majority of people searching the web go to their favorite search engine and start typing keywords. However, each engine uses its own methods for ranking results and may leave out results which you later find to be important. On the other hand, meta search engines submit requests to many primary search engines (such as Google, Yahoo, etc.) and gather a broader set of results, reducing the chance of missing important results.

What are meta search engines?
Meta search engines are either programs or websites that send requests to multiple primary search engines, combine the results together, and display them. They don't index the web or have a database themselves, because they ask the primary search engines for results.

How do meta search engines work?
Once you have typed in a word or phrase and started the search, meta search engines forward the request to many primary search engines. Since each primary engine has its own syntax for requesting results, meta engines modify the request for each individual primary engine.

Meta search engines usually send requests out simultaneously. This way, the requests get processed in parallel, saving time. Some meta engines can only get one, or at most several, pages of results from each primary engine. A few meta search engines can get as many results from a primary engine as that engine can supply, very helpful if you’re doing an in-depth search.

Once all the results have been received, the next step is to eliminate duplicate results and display

them, usually sorted by the engine that supplied the result, the rank of the result, or the relevance of the result. Some meta search engines can resort results based on user preferences.

What are the disadvantages of meta search engines?
1. Timeouts or long waits may occur if the meta search engine is having difficulty contacting the primary engine.
2. Many meta search engines only get the top 10 to 50 results per primary engine.
3. Some advanced features (ex. phrase searching) may not be available.
4. Many meta search engines exclude one or more of the major primary search engines (Google, Microsoft, or Yahoo).

Each meta search engine has its own way of dealing with these problems. In fact, one way of ranking meta engines is to go through this list and see how well each one is able to handle each of these objections.

What are the advantages of meta search engines?
1. Searching with many primary search engines often finds results missed by a single primary engine.
2. Requesting results from many primary engines in parallel saves time.
3. Eliminating duplicate results also saves time.
4. Getting results from many different primary engines provides opportunities to explore how to best combine the separate result lists.

The problem of how to combine lists of results from different search engines provides an opportunity to use sophisticated methods to help rank, index, and cluster results so the most relevant results can be easily found. This is an ongoing research area and methods such as latent semantic analysis have been developed to help solve this problem.