Over the past few years, enterprise software vendors have ventured well beyond their traditional focus on licensed software packages. Many have begun to offer solutions that incorporate such diverse approaches as open source software, service-oriented architecture and software-as-a-service.

Some software vendors even have taken a bold step into the world of hardware, and are offering appliances that integrate software with CPU, storage and other hardware to deliver function specific, performance-optimized solutions for quick deployment.

The appliance wars are upon us, as can be seen in IT vendors' eagerness to slap the label on a growing range of hardware-integrated solutions, most of which are much bigger than a bread box and far more complex and costly (though less so than the software-centric solutions they hope to supplant).

Appliance hype is building to a fever pitch. Every vendor claims its appliances are plug-and-play solutions, though few customers are so naïve as to imagine that a complex IT solution can be as easy to install and set up as,for instance, a toaster oven.

In addition, vendors and industry observers are starting to line up behind competing definitions of what constitutes a true appliance. Depending on whose religion you subscribe to, an appliance must be a simple device (such as a blade), or it can be a complex assemblage of processing, I/O, storage and other components integrated across one or more racks in an enterprise data center.

There are plenty of opportunities for overzealous vendors to stretch the concept of an appliance to the breaking point. Unfortunately, one of the core features that most people associate with appliances -- their physical tangibility -- is starting to fall by the wayside. Increasingly, vendors are exploring the notion of the virtual appliance, a self-contained software package that can be deployed rapidly to diverse operating and hardware platforms through virtualization technologies such as VMware and Xen.

Appliances are here to stay, and they are moving into the mainstream of enterprise computing and networking.

Many IT professionals have taken a first foray into this new world, in the form of content-aware network appliances from such companies as Cisco, Juniper Networks, F5 Networks, Citrix and IBM.

Just as important, appliances have begun to take up permanent residence at the heart of the data center, in the form of data warehouse appliances. In the past few years, such data warehouse appliance pure-plays as Netezza, DATAllegro and Greenplum have seen their market share grow. Even longtime software-oriented data warehouse vendors, such as Teradata, Oracle and IBM, have begun to offer integrated solution packages for appliance deployments.

These trends have been developing for several years, but the appliance market reached a turning point in March when IBM announced it had rearchitected its entire data-warehouse product family as appliances.

That same week, business-intelligence market leader Business Objects announced it was putting appliances at the core of its strategy. To develop business intelligence, data warehouse and data integration appliances for various customer segments, Business Objects is partnering with complementary vendors ranging from large established server and storage providers to pure-play appliance start-ups.

Appliances will have an impact on every component of the enterprise application architecture. If nothing else, the need for incrementally scalable application-infrastructure components will continue to grow, stoked by relentless increases in transaction and data volumes across the service bus. Enterprise IT professionals should begin now to factor appliances into their SOA strategies.