Ajax Components History

AJAX Introduction

Ajax is the acronym for Asynchronous JavaScript and XML. However, rather than functioning as an acronym it better describes a technique for producing faster, more interactive, and usable web pages that don’t require re-loading every time a user changes a request. This is accomplished by increasing web page responsive-ness through the exchange of small pieces of data by an invisible server.

The prerequisites of Ajax are a collaboration of HXTML (Extensible Hypertext Markup Language), CSS (Cascading Style Sheets) that help represent the markup language, client-sided description languages like JavaScript, objects like XMLHTTPRequest that allow the asynchronous transfer of data, and the formatting provided by XML (Extensible Markup Language).

Again, Ajax is a technique, not an object. Jesse James Garrett coined Ajax in 2005 in a presentation to clients. The components that make up Ajax existed well before they were implemented to increase web page usability. This article will describe the development of the components that make up Ajax and their uses.

AJAX Background

As aforementioned, the components that provide the framework for Ajax execution include the following: 1) HXTML, that blends HTML and XML functions, 2) Cascading Style Sheets (CSS) that present markup languages intelligibly and style web content, 3) client-sided description languages like JavaScript, 4) XMLHTTPRequest objects.

HTML (Hypertext Markup Language) is the primary markup language for web pages. Markup languages represent text and extra information about the text that corresponds to structure and presentation. Originally conceived by the on-line publishing industry to interact with manuscripts, markup languages transitioned into the digital age through HTML. HTML describes the structure of certain web page text and further complements that description with interactive forms and objects that affect web browser behavior.

XML (Extensible Markup Language) is considered a general-purpose markup language. XML is an open, standard language that facilitates data sharing across information systems, particularly those connected via the Internet. The latest version of HXTML 1.1 became a W3C (World Wide Web Conference) recommendation and, therefore, an industry standard in 2001.

CSS (Cascading Style Sheets) display the presentation of markup written document. This style sheet language, which is also standardized by W3C, presents structured documents whose content is reusable in a variety of contexts. Content can be attached to different logics to create different presentations of the same data. Style sheets have existed since the 1970’s and SGML (Standard Generalized Markup Language). CSS Level 1 became usable in 1996. By 1998, CSS Level 2 was W3C recommended. As of 2006, CSS Level 3 is still under development. The main CSS contribution allows a document’s style to be influenced by multiple style sheets. The cascading effect comes from the ability of style sheets to ‘cascade’ from one another, inheriting a stylistic mixture determined by the site designer and user.

Javascript is a scripting language created to enable prototype-based programming. It is most popularly used for web sites. Its only similarity with Java the programming language is its C syntax. Javascript was developed in 1995 and trademarked by Sun Microsystems. It was licensed for use with Netscape Communications when Netscape began to support Java technology in its Netscape Navigator web browser. Currently, Javascript also operates for other entities like the Mozilla Foundation. As of 2006, the latest model of this scripting language is Javascript 1.7.

XMLHTTPRequest object allows for the asynchronous exchange of data between the server and the client. It is an API (application program interface) that uses Javascript to transfer text data like XML using HTTP (hypertext transfer protocol) thereby establishing independent communication between the server-side and client-side of a web page. Microsoft developed it in 2000 as a part of Outlook Web Access. Mozilla incorporated XMLHTTPRequest in 2002 and Apple incorporated it into Safari 2.1 soon after.

AJAX Usage

The uses of these Ajax components work together to allow for automatic, user-based alterations of web pages. As an application of HTML in XML, XHTML allows for automated web processing through the use of the standard XML library. CSS is primarily used to stylize web pages and making them more easily understandable to users. Javascript allows accessibility to the DOM (Direct Object Model) to allow for dynamic information presentation and increased interactivity. The DOM is a standard object model that renders HTML, XML and other related formats. XMLHTTPRequest is important in Ajax web development techniques to increase web page responsiveness and interactivity. For example, it is currently used in Google’s Gmail services and MapQuest among other highly interactive sites.

Points of Interest

The technologies outlined above work together to comprise Ajax programming. The primary benefits of this suite of technologies allow users to access and create web applications more quickly with a level of responsiveness usually attributed to desktop applications. This increased responsiveness is coupled with increased interactivity that doesn’t make it necessary for the web page to reload every time a user makes a new request of the web application.