In my last column ( http://www.ebizq.net/hot_topics/soa/features/7051.html), I introduced the concept of SOA devices and outlined some historical precedents for them. I also outlined how, as SOA becomes more prevalent, it makes sense for selected SOA functionality to find its way into packaged and automated hardware-based solutions, much like software-based routing capabilities have evolved into routers or security software into firewalls.

This week, we’ll take a closer look at the potential range of SOA appliances that might come in useful for organizations implementing SOA, as well as contemplate why some organizations might want to consider SOA appliances. Let’s start by taking a closer look at the types of specialized HW that can be helpful for processing in a SOA environment.

The first type of device, and the one that’s been around the longest, is the category of XML accelerators. XML accelerators are dedicated devices that offload XML processing. For example, you could have XML messages flowing through a network and you might want to make sure they’re validated against a schema. Using an XML accelerator can be more economical than a traditional server for that type of requirement. Another scenario where XML accelerators can help would be if you’re using XSLT or trying to convert XML into HTML for a portal application, for example. XML accelerators are also applicable for compressing XML, format conversion and parsing. XML accelerators basically sit as proxies between the requestors and senders of messages, and as the messages flow through, the schema validation, compression or other XML-related function takes place.

A second category of SOA appliances is the XML router category. XML routers are focused on high speed content-based routing, whether it’s routing proprietary protocols or XPATH or other standards. XML routers enable the routing the delivery that’s independent of producers or consumers and operates at the message layer, for example—for every purchase order over $50,000, route this message to server A, otherwise, route to Server b. Organizations should consider XML routers when there’s a need for message enrichment, such as adding specialized headers or time stamps or adding the route that the message took to get to the final destination.

The next category of devices to consider is XML security gateways or XML firewalls. Because organizations are now starting to use this new layer of XML connectivity to communicate and exchange message with organizations or individuals outside the corporate IT boundaries, there’s actually a need for new types of threat protection and new security capabilities provided by XML security gateways. Using a hardware device such as an XML security gateway to enforce security policies can be particularly helpful, since it can be in a separate domain, and controlled by a separate group, such as a security group. It can also provide a greater level of performance and do more security checks without compromising the end-to-end SOA performance.