Does Desktop Virtualization Need Desktop SOA?

Part of the rationale for Web services has always been that theycan tunnel through firewalls, linking networks that are otherwisesecurely separated. Virtualization puts up similar barriers betweenapplications within a single machine, so will crossing them requiresimilar technology?

Startup OpenSpan says that it will. This week, it launched what it calls SOA Desktop Edition,software that the company claims can give almost any Windowsapplication a full Web services API. OpenSpan promotes its product asthe "the last mile of SOA", but that slogan's already taken(by several rich Internet application companies, on the basis thatAjax works better if browser-based apps link into a full SOAinfrastructure on the back end.) A more accurate description would bea scaled-down SOA, as for it to be useful each PC would end uphosting (and consuming) multiple Web services.

So why run Web services on the desktop? According to OpenSpan, thesame reason that you'd run them on  a server – namely, forstreamlined application integration and data sharing. SOA DesktopEdition grew out of a previous product called Integrator, whichtracked how every application accesses Windows' APIs and letdevelopers intercept API calls while building mashups. For example,one app's menus can be made available through another, or complexoperations that otherwise involved multiple copy and pastingoperations can be automated.

Like the Windows API itself, Integrator was designed to mix appsinstalled on the same machine. Converting desktop Windows apps to Webservices makes them accessible anywhere, potentially letting users onone PC automatically access APIs on another. It also means thatservices from Windows apps can be orchestrated into newcomposite apps using standard SOA tools from vendors like IBM andBEA, or combined with components based on Java.

Not everyone will think exposing desktop apps as Web services is a great idea. Security-conscious users may be put off byWeb services' original firewall-tunneling feature – somethinguseful in closely monitored and locked-down server apps, but perhapsmuch riskier than when let loose on ordinary PCs. That's whyOpenSpan's vision doesn't involve desktop Web services accessed byusers across the Internet, or even predominately by other machineswithin the LAN. It foresees the main consumers of desktop Webservices being other VMs running within the same PC, accessingfunctionality that right now is available through standards WindowsAPIs – everything from file load and save to compositeapplications.There's one obvious problem with this: Right now, most of usaren't running VMs on our desktops, and even most of thevirtualization vendors seem focused on servers. However, all thehardware-assisted virtualization technology that Intel and AMD buildinto their server chips also is going into desktops (and laptops),even it isn't used at present, while applicationvirtualization has attracted a growing following. Most vendorsalready implement their own ways to share data, with app virtualization preserving functionality like the clipboard. So it's probably inevitable that virtualization will migrate to the desktop, even if Web services might not.