1. Important definitions
A database is a structured collection of records or data. A computer database relies upon
software to organize the storage of data. The software models the database structure in what are
known as database models. The model in most common use today is the relational model.
Other models such as the hierarchical model and the network model use a more explicit
representation of relationships (see below for explanation of the various database models).
A Web search engine is a search engine designed to search for information on the World
Wide Web. Information may consist of web pages, images and other types of files. Some
search engines also mine data available in newsgroups, databases, or open directories. Unlike
Web directories, which are maintained by human editors, search engines operate
algorithmically or are a mixture of algorithmic and human input.
Generally, a directory, as used in computing and telephony, refers to a repository or database
of information which is heavily optimised for reading, under the assumption that data updates
are very rare compared to data reads. Commonly, a directory supports search and browsing in
addition to simple lookups. A website which offer access to a categorized listing of other
websites optimized for lookup, search, or browsing is a directory, a web directory.
A web directory or link directory is a directory on the World Wide Web. It specializes in
linking to other web sites and categorizing those links. A web directory is not a search engine,
and does not display lists of web pages based on keywords, instead it lists web sites by
category and subcategory. The categorization is usually based on the whole web site, rather
than one page or a set of keywords, and sites are often limited to inclusion in only one or two
categories. Web directories often allow site owners to directly submit their site for inclusion,
and have editors review submissions for fitness.
A website (alternatively, web site or Web site, is a collection of Web pages, images, videos or
other digital assets that is hosted on one or more web servers, usually accessible via the
Internet. A Web page is a document, typically written in HTML, that is almost always
accessible via HTTP, a protocol that transfers information from the Web server to display in
the user's Web browser. All publicly accessible websites are seen collectively as constituting
the "World Wide Web".
The pages of websites can usually be accessed from a common root URL called the homepage.
The URLs of the pages organize them into a hierarchy, although the hyperlinks between them
control how the reader perceives the overall structure and how the traffic flows between the
different parts of the sites.
Some websites require a subscription to access some or all of their content. Examples of
subscription sites include many business sites, parts of many news sites, academic journal sites,
gaming sites, message boards, Web-based e-mail, services, social networking websites, and
sites providing real-time stock market data. 1
1 From Wikipedia, the free encyclopedia http://en.wikipedia.org/wiki/Main_Page viewed
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