Users search an index of web pages through a query box or a template that often looks like this (ps. this is a dummy example!)
Documents in which the search terms occur will be returned as "hits." There are three parts to a search engine: one part identifies web pages to be included in the database, one part that indexes the sites and a searching mechanism with an interface, which scans, for keywords within the index.
Although some facilities incorporate "natural language" searching (searching by asking a question "Where are the doughnuts?"), most search tools retrieve "hits" or "matches" by seeking occurrences of your search terms within its database and by attempting to match the terms against its index.
When do I need to use one ?When you do not know the address of the web site you are looking for, or if you are doing a subject search on the Internet.
How do I narrow down my search
Each search engine uses a slightly different searching method . But you should be able to try one of the following ways on most:
1. Doing a title search:
The majority of commercial search engines like Alta Vista will accept the formula title: before the search term. This will give you only web pages with that word in the title of the web page. For example:
will normally give you web pages that have the word 'doughnuts' in the title of the document you are looking for.
2. Ranking your search
Each search engine uses a different algorithm or method to calculate something called a "relevance" which it "ranks" the hits that it gives back to you in order or relevance. This is most useful if your search has returned a large number. You can also limit your search by date or by language on some search engines.
3. Boolean searching.
Many search engines will have an Advanced search option that allows the use of "boolean" operators – OR, AND, AND NOT and NEAR. These can be used to create relationships among the keywords in your search query. Using these expressions allows you to tailor your search to find exactly what you are looking for.
|
Expression |
Symbol |
Action |
|
AND |
& |
Finds documents containing all of the specified words or phrases e.g. peanut AND butter finds documents with both the word peanut and the word butter. |
|
OR |
| |
Finds documents containing at least one of the specified words or phrases. Peanut OR butter finds documents containing either peanut or butter. The found documents could contain both items, but not necessarily |
|
AND NOT |
! |
Excludes documents containing the specified word or phrase. Peanut AND NOT butter finds documents with peanut but not containing butter. NOT must be used with another operator, like AND. AltaVista does not accept 'peanut NOT butter'; instead, specify peanut AND NOT butter. |
|
NEAR |
~ |
Finds documents containing both specified words or phrases within 10 words of each other. peanut NEAR butter would find documents with peanut butter, but probably not any other kind of butter. |
|
|
|
Use parentheses to group complex Boolean phrases. For example, (peanut AND butter) AND (jelly or jam) finds documents with the words 'peanut butter and jelly' or 'peanut butter and jam' or both. |
This page last updated by John McMullan.