Although we tend to talk just about "search engines" there are in fact four quite different types each having its own particular use.

They are:

Search Engines

Standard Search Engines are the ones with which you will be most familiar, they include Google and Altavista. They automatically look through many thousands of web pages by indexing the keywords contained on them. So, if you ask Google to search for food it will look at the first two hundred words on each of its millions of pages and list those which include the word food.

Pages which contain the word food more than once will be placed at the top of the results list; and pages which also have lots of other pages linking to them will be placed near the top of the list. (This is because a page which is linked to by many other pages is assumed to be more useful and popular).

Search engines that work in this way return so many hits and present you with so much data that it can be difficult for you to work through the information. Even though these tools find such colossal amounts of information it is estimated that no single search engine of this type can ever look at more than about 40% of the web!

Other standard search engines that are well worth using include Teoma and Ask Jeeves.

Metasearch Engines

Metasearch engines work differently from the standard search engines listed above.

The main difference is that they are able to search across a number of different search engines at the same time. This means that instead of searching for food just using Google you can use perhaps ten, twenty, thirty even hundreds of different search engines together.  The obvious advantage of these tools is that you can search a much greater portion of the web for no extra effort on your part!

Some of the better known and well used metasearch engines are Dogpile and Metacrawler.

Probably the best of the metasearch engines is Wisenut. Wisenut organises your search results into categories, lists these categories at the top of your results page and tells you how many hits you have in each category. For example, a search for "food" generates categories such as food safety(16 hits), food service (3 hits), food science (15 hits) and so on; this means that you can go directly to the most relevant section of results and ignore useless hits. Wisenut has two other useful features. Firstly, it tells you if a site has paid a fee to be included in your list of results by labelling it a "sponsored listing." Secondly, there is a "sneak-a-peek" facility which allows you to take a quick look at a site without leaving your results list or waiting for the whole of the site to open.

Classified Directories

A classified directory is compiled by a person, it is not an electronically generated list. It is basically a list of resources arranged under subject headings. Each heading is divided into narrower headings and this process is repeated several times so that you can browse through the site and find what you are looking for. (Most directories also include a search facility which allows you to type in a search term).

The example that you will be most familiar with is Yahoo!

In Yahoo! you will see a whole range of subject headings that you can browse and gradually narrow down the list of available resources until you find what you want. For example you might click on "Health" and chose from the list to look at "Alternative Medicine." From there you might chose to look at "Aromatherapy"  and then go to a site advertising aromatherapy products.

Classified Directories do not search the web pages for keywords (like Google or Altavista) they list catalogue records and search through those. They tend to return fewer hits but the material that they do find is of high quality because it has been pre-selected by someone.

Subject Gateways

Subject Gateways are classified directories dealing with one specific subject.

They contain high quality resources that have been selected by subject specialists and there are far too many of them to list here. Many of the sites listed in the Subject Links pages here fall into this category.

You can view an excellent collection of Subject Gateways at Pinakes.

Which one do I use?

These different search tools will affect both the amount and the quality of information that you find on the internet. So which one or which ones (because it may be necessary to use more than one service) should you use for your enquiry?

Use a Search Engine if: You have a very specific query, or if you need lots of information. Use a Metasearch Engine if: You want to increase the proportion of the web searched Use a Classified Directory or Subject Gateway if: You have a general information need, or you would like to browse through structured information, or you want high quality information.

Sometimes you may find that a search does not return all of the hits that you expected, you might feel that it has missed something that you know is there. There are many reasons for this; perhaps a site is too new to be picked up by the major search engines, maybe the information is in a database that is not normally accessible to search engines or possibly the information has been archived. If this is the case your final strategy should be to use The Invisible Web search engine. This is a directory of 10,000 databases, archives and search engines containing information that is frequently missed by more traditional searches.

Useful Tips

Most search engines are now beginning to standardise the symbols that they will respond to and you will find these three to be the most useful: the plus sign +, the minus sign -, and inverted commas "".

Using the plus sign forces the search engine to find pages that contain all of the listed search terms; Russian+Revolution will find pages that contain both of these words, though they will not necessarily be next to each other. For example you might find a page about the industrial Revolution in Eastern Europe and Russia.

Using the minus sign forces the search engine to ignore pages which contain the word following the minus sign; Russian+Revolution-industrial will find pages that contain both of the words Russian and Revolution but will ignore pages that contain Industrial even if they also contain Russian and Revolution.

Using inverted commas or quotation marks forces the search engine to find only pages which contain the exact phrase enclosed in the quotation marks; "Russian Revolution" or "Industrial Revolution" for example.

Although I have used some capital letters here it is worth pointing out that nearly all search engines are not case sensitive; that means that it does not matter to them whether you use capital letters or not. Great Britain, great britain, GrEaT BrItAiN should all return the same results.

Finally, if ever you need a search engine and you cannot remember any of their addresses simply click in the address bar at the top of any web page and delete the internet address or url then type in the keyword that you would like to search for. Since a keyword or phrase looks nothing like an internet address the machine will automatically default to Micrsoft's search engine and run the search for you. After a few seconds you will be shown a page of results just as if you had used your favourite search engine!

(If you would like to complete a more detailed tutorial have a look at the Internet Detective; as well as helping you to use the internet this tutorial will also help you to evaluate the quality of websites.)

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