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Dynamic Web pages can be defined as: (1) Web pages containing dynamic content (e.g., images, text, form fields, etc.) that can change/move without the Web page being reloaded or (2) Web pages that are produced on-the-fly by server-side programs, frequently based on parameters in the URL or from an HTML form.
Web pages that adhere to the first definition are often called Dynamic HTML or DHTML pages. Client-side languages like JavaScript are frequently used to produce these types of dynamic web pages.
Web pages that adhere to the second definition are often created with the help of server-side languages such as PHP, Perl, ASP/.NET, JSP, and languages. These server-side languages typically use the Common Gateway Interface (CGI) to produce dynamic web pages.
The word dynamic is used in opposite to static; see Static Web page.
Client-Side
Client-side dynamic content is generated on the client's computer. The web server retrieves the page and sends it as is. The web browser then processes the code embedded in the page (normally JavaScript) and displays the page to the user.
The innerHTML property (or write command) can illustrate the "Client-side dynamic page" generation: 2 distinct pages, A and B, can be regenerated (by an "event response dynamic") as document.innerHTML = A and document.innerHTML = B; or "on load dynamic" by document.write(A) and document.write(B).
The problems with client-side dynamic pages are:
- Some browsers do not support the language or they do not support all aspects (like write command and innerHTML property) and of the language.
- The information cannot be stored anywhere but the user's computer, so it cannot really be used for statistics gathering.
- Search engines are not able to run client-side languages and cannot crawl links generated by them.
- Some users have scripting languages disabled in their browsers due to possible security threats.
Ajax is a newer web development technique for creating client-side dynamic web pages. Google Maps is an example of a web application that uses Ajax techniques.
Server-Side
Server-side dynamic content is a little bit more complicated.
- The browser sends an HTTP request.
- The server retrieves the requested script or program.
- The server executes the script or program which typically outputs an HTML web page. The program usually obtains input from the query string or standard input which may have been obtained from a submitted web form.
- The server sends the HTML output to the client's browser.
Server-side has many possibilities for dynamic content, but the use of it can be a strain on low-end, high-traffic, machines. Some websites use the Robots Exclusion Standard to keep web crawlers from accessing dynamic pages for this reason. If not properly secured, server-side scripts could be exploited to gain access to a machine.
Virtual Documents
"Virtual documents" are web documents for which the content, nodes or links, or all three, are created as needed.*
It would appear that Wikipedia may have addressed some of the research issues raised by virtual documents (in the contexts of digital libraries / information retrieval (?) ).
See also
"Dynamic Web page"