About Subject Directories & Search Engines

Subject directories compared to search engines.....

Subject directories group web sites into subject categories and sub-categories which you can browse to find links to web sites of interest. 

• True directories are compiled by humans.  
• Web site owners/managers can ask to have their sites included in a subject directory. Less selective subject directories will accept most submitted sites.
•   Subject directories with more stringent quality standards will be more selective and will, therefore, more consistently lead to better quality material. Selective subject directories must be created by humans because computers cannot evaluate the quality of the web sites.

A search engine, on the other hand, consists of a a large database created automatically by a "robot" that travels the 'net on a regular basis. 

• The resulting database is searched by the engine when you submit words to be searched. 
• A search engine will frequently provide subject categorization of the sites in its database. This may look similar to a selective subject directory, but no selection for quality is involved in this process. The links in the database are simply organized into subject categories.

When to use a subject directory....

Browsing or searching a subject directory provides an effective alternative to using search engines when researching broad topics. Search engines would retrieve an unmanageable number of results in a search on a broad topic. Directories, because they include fewer items, will generally yield fewer items. 

If you are looking for the best sites for a specific purpose, selective subject directories are particularly helpful since they have evaluated the sites.

When to use a search engine....

On the other hand, search engines can be more effective when searching narrow topics.   Because subject engines include any web pages in their databases, they are more effective when looking for very narrow topics or for specific people, organizations, etc.

Searching with subject directories....

The subject directories are designed to be browseable -- allowing you to move from link to link to get from a broad subject category to narrower and narrower subcategories.  

In addition, most directories have a "search" feature which saves you from navigating from category to sub-category to sub-sub-category (and so on) within the directory. The search feature lets you jump directly to the relevant topic area in the directory.

Searching with search engines....

To improve your search results:

1. Search more than one search engine...

because different search engines produce different results.

2. Try other search engines when your "favorites" fail...

because the "best" search engine may be different for different searches.

3. Read any search tips, help, or instructions...

because techniques for searching vary from search engine to search engine.

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1. Different Search Engines Produce Different Results

When you submit words that describe your topic to a search engine, the search engine retrieves a list of sites from its database that match your request.

The databases of search engines differ from each other.  They are created by robots which have followed different paths across the web and used different rules for finding web sites for inclusion in their databases.  The database information may have been created from information in any or all of the following areas of the pages:  web page titles, URLs (web page addresses), web page content (text & images), and links on the web page. 

Because the robots of the various search engines start in different places and work in different ways, different search engines will produce different results.

2. Best Search Engines

While one search engine may perform very well for one search, it may perform very poorly.  These differences arise because of the topic being searched, the nature of the information needed, the size or contents of the database being searched, or for other reasons.

The "best" search engine is the one that works, so be flexible about trying a different search engine when your favorite search engines fail.

 

3. Techniques for Searching Vary from Search Engine to Search Engine

Each search engine has its own rules for entering searches. Some allow you to combine words using the connectors AND, OR or NOT while others do not. Some allow the use of punctuation to indicate phrase searching, and so forth.

When you select a search engine, find out how to search by looking for "help", "instructions", "search tips" or some other related phrase that leads to instructions for searching.

Taking time to find out a search engine's searching rules can significantly improve results.

            Search Techniques to Improve Search Results

Do not assume that every search engine allows the techniques that are described below, so be sure to look for "help", "instructions", "search tips" before using the techniques in a new search engine.  

             1.      Use the plus sign ( + ) to require that certain word(s) be in every                     document retrieved. 

Examples: 
+dyslexia  +reading  +assessment
+grammar  +usage
+telescopes  +construction  +home

2.      Use the minus sign ( - ) to require that certain word(s) not be in every document retrieved. 

Examples:
+apples  +varieties  -computers 
+guns  -hunting

3.      Use quotation marks ( “ “ ) to require that words be next to each other in every document retrieved

Examples:
“attention deficit hyperactivity disorder”
“National Education Association”

             4.      Combine the techniques….

                         Examples:
                        +”attention deficit hyperactivity disorder”  +diagnosis
                        +”running shoes”  +reebok  +adidas  -nike