I have had a go at defining infrastructure architecture and the feedback seems to have been: Ok, so what about infrastructure architects and the business value of infrastructure rather more than the details of what categories exist within infrastructure architecture. There also has been significant pushback on coining terms so I wont do that (anymore).
Thinking about the business value of infrastructure it is clearly significantly different from Solutions or applications architecture where the application is designed to support a particular business need or project. The value of the application is very closely tied to the value of the business project so it (reasonably) easy to quantify. Infrastructure on the other hand isn't aligned to a specific business need but more to the whole enterprise. In addition its quality attributes are much less about function and more about attributes such as availability, scalability etc which are much harder to measure and put value to.
Infrastructure architects are architects who are focused on the architecture of the infrastructure of an organization. Actually there are not many people who have infrastructure architect as their title, in many cases it is the IT manager, CTO or even CIO who performs this function. I blogged earlier about the other titles in the infrastructure space and clearly the relationship between the infrastructure architecture and these people (and indeed the business people) is key. The question then is what are the attributes that an infrastructure architect has or needs to have. I am in the process of defining this for the Microsoft Architect Certification so will blog about that separately.
These are both key topics in the infrastructure architecture space so I will return to elaborate on them in more detail.