Web Services and Client Server Technology
Introduction to Distributed Computing
The Internet and expanded network connectivity established client-sever models as the preferred form of distributed computing. When talking about Client-Server models of networked communication using web services the broadest components of this paradigm become the web browser (functioning as the client) and web server. So by introducing web services into the equation, client/server models become browser/server models.
These models are Server-Centric, which make applications easy to load and install, but reduces rich user interaction. Server-Centric applications are currently available from standard browsers, making them convenient and popular with developers. Therefore, a way of enriching user experience is an essential frontier that must be developed for using browser/server models of distributed computing.
One of the revolutions of the personal computer was usability or the ease with which humans could communicate with and configure their computers. This usually occurred through individual configuration and the user interface (UI). Administratively, this was a nightmare because administrators had to install and maintain applications one machine at a time and manage multiple platforms. Individual installation and maintenance across platforms made web services seem like a good solution. Using HTML tools, developers moved toward giving applications global potential and a uniform protocol for management and deployment.
The evolving trend was for developers to create applications that run on the server side, while web browsers became, for all intents and purposes, the standard client interface. Client processing power atrophied as execution of programs took place on central servers and output or responses were transmitted back to the browser through standard IP (Internet Protocols). This improved installation, administration, and maintenance. However, to be intelligible to the wide-array of platforms being targeted, web developers had to write in the lowest common denominator or the most widely accepted standards. This affected user experience negatively, while ensuring that applications could be deployed to the most users.
Once the benefits of browser/server models were cemented into place vendors looked to improving user experience to give their products a competitive edge. After all, how many everyday users would buy applications that were pitched as easy for developers and administrators but cut into their user-friendliness?
Rich client applications were already part of personal computer systems. However, the focus on server-centered application meant that a lot of client-side processing power was going to waste. This article will discuss how balanced computing that takes advantage of both client (in this case, browser-as-client) and server capabilities and web services combine to improve user experience.
Web Services and Client-Server/Browser-Server Technology
Web services and Client-Server technology made it possible for applications to integrate of separate components. These components might exist on separate machines, but they work together through network (Internet) communication. Applications using web services demonstrate the integration of components coming from multiple sources. This makes version management important. One of the benefits of having to focus on version management is to make developers aware of component dependencies and specific areas that require maintenance in each version. This allows developers to customize maintenance for application deployment. These distributed application components use universal formats provided by such programming languages as XML (Extensible Markup Language) and WSDL (Web Standard Description Language).
XML is the W3C standardized language that allows information and services to be written in a structurally and semantically intelligible way that both humans and machine on different platforms can understand. It can be customized with user or industry tags. WSDL uses an XML format to describe network services. These service are described as endpoints that use messages to transmit documents or procedure-oriented information. These operations and messages are abstract, but then they are attached to specific network protocols and message formats to enable communication. Distributed application components also use universal protocols like HTTP (Hypertext Transfer Protocol) and SOAP (Simple Object Access Protocol).
HTTP is the standard protocol for transmitting HTML files or documents. SOAP is a message-based protocol formatted in XML and using HTTP. It is a way for a program running in one operating system to communicate with a program running in another. For the purposes of this discussion, applications that take advantage of web services will be understood as ‘balanced computing model’ because these applications are designed to take the fullest advantage of both client and server capabilities in the most efficient way. This model of balanced computing improves traditional Client-Server model by not stressing one part of the system and ignoring the capabilities of other parts.
For example, traditional browser-server models were Server-Centric. They could handle user demands but did not take advantage of client-side processing that could predict user behavior. To predict the behavior from a diverse customer base requires headroom. Headroom is also known as the attenuation crosstalk ratio. It ensures the network connections are strong and that signals on the receiving end of a communication are strong enough to overcome any interference. This provides a consistent and customized user experience regardless of unpredictable behavior in the network.
Balanced Computing and the Server’s Changing Role
In balanced computing, processing is shared between clients, servers, and any other devices connected via a network. This distribution is inherent in the design since applications are already spread out on different machines and connected through web services. In balancing, the processing required by each new use is often shifted back to the user’s system, thereby taking fuller advantage of client-side processing power. This allows for improved scalability since the processing load is increased insignificantly by the addition of users.
Load balancing can also be achieved by building service-oriented applications (SOAs) where components run on different nodes in multiple locations duplicate services on multiple nodes. This duplicating of services on multiple nodes also improves reliability since there is no single point of failure that will topple the entire application. Through balanced computing, platforms can take maximum advantage of computing and display capabilities on each platform. The virtual application which is balanced across multiple nodes remains transparent (its complex functions hidden) while the user utilizes his or her own collection of devices to run and view the application on the user end.
Balanced computing not only distributes the processing load, but changes the role of the server as well. Instead of computing so heavily, the server primarily directs traffic. Given rich clients and decent Internet connectivity, users directly contact databases instead of requiring server intervention. Rich clients are applications in user computers that retrieve data through the Internet. As previously discussed, the proliferation of web-based applications replaced the user interface with the web browser. Scripting languages, like JavaScript or VBScript, were embedded into HTML to improve user interfaces (among other things). Java applets were also added. But nothing could compete with the user experience of using an application built from its local environment. Developing technologies like improved web-page scripting languages and AJAX (Asynchronous JavaScript and XML) made web browsers function more like rich client applications.
Another method used to reduce demands on the server uses a connecting device to re-direct previously server-side processing to the client. This depends on the client device capability and Internet connectivity. If these are weak, the server picks up the slack, making application performance consistent on both the client and server ends.
User Experience and Development
Balanced distributed computing models improve user experience and expand development. Developers can focus on user experience by examining devices and customizing features. For example, different user interfaces can be customized for different departments that require different resources to perform their function. Different roles would have their own user interface. Well-defined user roles and profiles that are stored on user machines make more efficient use of server computation. It allows the server to pull customized responses based on the identity/role of the user. To further reduce server demand, clients can communicate directly with databases by requesting information for the user role profile. This eliminates the web server as middleman for the request and computation on the output side.
Data integration on user platforms offers new opportunities to build applications that draw data from a variety of sources and can add different contexts. In a balanced distributed computing model, web services send information that is usually stored on databases or servers (like financial information) to the user’s machine. It accomplishes this by using the client-side’s processing power. These responses are formatted in the increasingly popular, universal XML. Desktop applications (on the user’s system) can take that information and analyze it in different contexts.
The decentralization of distributed browser-server models also improves security and protects privacy. For example, data repositories are often located in a different location from the server. This makes it more difficult for external attackers to find. It also makes it less accessible to internal attackers. Also, it is safer for user profiles to be stored on individual machines, rather than on a central database.
Distributed computing models address the future of IT architecture and application. Organization must aim to create independent and flexible applications that can respond quickly to a variety of contexts. Connections must be agile. Loosely coupled applications, characteristic of distributed computing models, withstand broken connections and slow Internet performance. This protects core technologies from customer demands and lack of Internet bandwidth.
