Layer 4 - Application Infrastructure - Orange

The applications software of an organization represents a "make vs. buy" proposition. If you can buy a software package that meets your needs, why build one? As long as available products integrate relatively well with the rest of what you have, purchased, off the shelf items may cost less than a custom project and it will likely include support services. To the degree that the unique competitive advantages of the organization need to be modeled, there is less likelihood that answers can be found from outside of the organization.

Many applications used by organizations are functionally neutral. Email systems, desktop applications, web services servers, and other purchased software provides resources that other applications, including taxonomy tools, can use. Sitting "above" data stores, functional applications can make use of both databases and directories to provide functionality. This "middleware" layer must be rock-solid to avoid back door security problems.