Clients virtualize beyond recognition

Client virtualization is an underlying theme in many recent industry announcements. In virtualization, the external interface of every service becomes unmoored from its implementation in particular physical platforms, operating systems, application frameworks and software components.

Essentially, a client becomes virtualized when its graphical user interface (GUI) grows abstracted from the resources of the local access device, be it a PC, handheld or other computer.

The virtualized client may rely on both local and remote network resources to render its interface, furnish its processing power, store its data, route its print jobs and handle other core client functions. Users remain blissfully unaware of what blend of distributed resources is actually driving their presentation experience.

Vendors are avidly exploring ways to virtualize client environments. Take Microsoft Windows Vista, for example. Microsoft has removed most of the new functional components – including security and file-system enhancements – that were supposed to make Vista worth waiting for.

What’s primarily left is a client virtualization technology called Windows Presentation Foundation (WPF), which allows the Windows GUI to be dynamically rendered, tailored and customized by applications, in keeping with a declarative markup syntax called Extensible Application Markup Language (XAML).

Essentially, WPF/XAML enables a virtualized separation of the Windows presentation interface from the underlying application code.

Microsoft has even decoupled WPF/XAML from Vista, taking the Windows platform another step down the road to total virtualization. WPF/XAML, and all Vista features, also will be made available as retrofits for legacy Windows operating systems, including XP and Server 2003. This new technology will basically become the virtualized presentation layer to all Windows versions.

There’s even more to Microsoft’s client virtualization story.

Under the company’s Windows Live strategy, operating system and application features will be provided as hosted software as a service. Live is essentially aimed at making free Microsoft-hosted services – such as e-mail, instant messaging, search, file sharing, VoIP, software delivery and RSS aggregation – integral to Microsoft’s not-free client software.

When the client operating system goes “live,” per Microsoft’s strategy, it blurs the practical boundary between those functions the client performs from local resources and those it relies on the service fabric to accomplish.

But let’s not give Microsoft all the credit. Enriched browsers of all varieties are blurring the practical distinction between clients and servers even further.

Enriched browsers such as those supporting Asynchronous JavaScript + XML (AJAX) deliver a more GUI-like user experience than a basic browser. AJAX-capable browsers, such as Internet Explorer and Firefox, shift the presentation emphasis away from downloading individual Web pages toward navigating within richer, structured, client-side content caches.

The enriched browser can execute more application logic, cache more content and perform more rendering locally than a basic browser.

And it offloads some or all of these functions from portals, Web sites and other presentation servers.

Kobielus is a senior technical systems analyst at Exostar, a business-to-business trading exchange. He can be reached at

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