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Overview
Product Details
| ISBN-13: | 9781135516963 |
|---|---|
| Publisher: | CRC Press |
| Publication date: | 01/23/2001 |
| Sold by: | Barnes & Noble |
| Format: | eBook |
| Pages: | 288 |
| File size: | 4 MB |
About the Author
Read an Excerpt
Chapter 1: Introduction
To say that the World Wide Web has changed the face of computing is a vast understatement. In the first year or so of its existence, the Web was simply an interesting enhancement to the user interface of the Internet. Prior to the Web, the Internet was a network used heavily by government and educational institutions. The user interface of the Internet was character-based and cryptic, and therefore most users of the Internet were relatively sophisticated computer and network users. The Web offered a simple user interface and an easy way of interconnecting documents of related information. The Web technologies eventually evolved to support sophisticated interaction with users, which laid the groundwork for a new paradigm for transacting business. The Web has spawned entire new industries and has rendered the term "dot-com" a common adjective to describe the new companies and industries. The letter "e" (E) is being used to preface nouns, adjectives, and verbs and signifies the new electronic economy. The Web has created thousands of millionaires and billionaires from Internet initial public offerings (IPOs) and has leveled the playing field between new startups and established "brick-and-mortar" companies.Economists regularly use the terms "new economy" to describe stocks and companies that enable an Internet model of doing business, and "old economy" to describe stocks and companies that sell goods and services in the traditional manner. The new-economy companies offer products or services for conducting business-to-consumer (B2C) and business-to-business (B2B) transactions. Yahoo!, America Online, eBay, and Amazon.com are premier examples ofnew-economy companies. While the new-economy companies have received a lot of press and have been the darlings of the NASDAQ stock market, the old-economy companies are not standing still. Almost without exception, they all have some form of Web presence and many are making dramatic movements in embracing the Web model of doing business. Economists and stock analysts are now saying that the old-economy companies, with their vast resources, brand recognition, and distribution channels, are poised to overtake many of their new-economy competitors. In fact, some analysts predict that some new-economy companies will cease to exist once their more traditional competitors ramp up the Web parts of their businesses.
Computing architectures have been changing rapidly to accommodate the new Web model of doing business. An application server is a relatively new breed of product that allows enterprises to augment their Web servers with new applications that are comprised of new business logic. Many application servers also integrate transactions and data from mission-critical, legacy hierarchical and client/server systems. Application servers represent the marriage of architectures. They allow organizations to build, deploy, and manage new applications that are based on the Web model but that integrate a wide variety of existing systems. Exhibit 1.1 depicts the very general architecture of an application server.
Before the Web, computing architectures evolved over years or even decades. The mainframe dominated computing from the 1960s until the 1980s. The mainframe model dictated a hierarchical architecture in which the mainframe controlled all communication, and end-user devices (terminals) had no local computing power.
With the advent of the personal computer and the intelligent workstation in the 1980s, the client/server era of computing began. Early advocates of client/server computing giddily pronounced the end of the mainframe era and the hierarchical model. In reality, there were several issues (cost, complexity, platform compatibility, and proprietary interfaces) that prevented the client/server architecture from completely replacing existing hierarchical systems. By the early 1990s, object-oriented architectures were being developed and deployed to overcome some of the problems with traditional client/server programming.
Then came the Web. With its ubiquitous user interface (the Web browser) and low cost of entry, the Web model quickly dominated. Enterprises of all sizes began to deploy Web servers for public access over the Internet, employee access over corporate intranets, and business partner access over corporate extranets. Throughout this book, the term "i*net" will be used to refer collectively to the Internet, intranets, and extranets. I*nets are, by definition, based on Web and Internet technologies. This means that they utilize TCP/IP as the networking architecture, Web browsers as the means of accessing information and applications, Web servers as the entry point (or "portal") to the enterprise, and Internet standard technologies for security, name resolution, and application deployment.
The application server is a special breed of product that spans the decades, seamlessly integrating the variety of different systems and architectures that a typical enterprise has deployed, and providing enterprise access to all i*net users. The application server is based on object technologies and has interfaces to visual development tools, allowing brand new applications to be built much more quickly than in the past. The object orientation promotes the ability to reuse code and potentially to integrate off-the-shelf, commercially available components, enhancing time-to-market and code quality. Application servers represent the pinnacle of server-based computing that integrates the high availability and advanced security capabilities demanded by today's enterprises. Application servers, in summary, facilitate the implementation of enterprisewide E-commerce and E-business systems.
The Evolution of Computing Architectures
Most enterprises have built their IT systems, applications, and infrastructure over a period of many years. The mission-critical systems have been created and fine-tuned to run the key business processes of the enterprise with 99.999% availability. In many cases, the mission-critical applications run on legacy systems and there is no compelling justification to move the applications to Web servers. The vast investment in building and maintaining these systems, estimated at trillions of dollars, must be protected because the scalability and reliability of the mission-critical systems have been proven over time.
However, enterprises that wish to harness the power of the Web to their advantage must find ways to integrate the new with the old. Because of the massive installed base of legacy equipment, systems, and applications, a brief overview of the evolution of computing architectures as implemented in enterprises is provided here. This is not an idle diversion into ancient history. The Web architects of today may need to accommodate a variety of legacy systems, architectures, and technologies if they hope to achieve full integration of the Web with their key business processes.
Legacy Systems
The early business computer systems were mainframe computers. Early mainframes were extremely expensive and somewhat rare. Programs and data were encoded on punched cards or tape and read into the system...