Almost all of the directories around today are general in nature and include sites across a variety of categories, countries and languages. Sometimes niche directories give attention to restricted regions, single languages, or specialist sectors. One type of niche directory with numerous sites in existence is shopping directories. Shopping directories are experts in the field of listing of retail e-commerce sites.
Types of well-known general web directories are Yahoo! Dir plus the Open Directory Project (ODP). ODP is significant because of extensive categorization and large amount of listings as well as its free availability for proper use by other directories and engines like Google.
Yet , a debate within the quality of directories and databases still continues, as engines like Google use ODP's content without real integration, and several experiment using clustering. There were many attempts for making directory development easier, for example using automated submission of related links by script, or any type of amount of available PHP portals and programs. Recently, social software techniques have spawned new efforts of categorization, with Amazon. com adding tagging with their product pages.