|The new VISTA Onion Diagram, grandchild of Tom Munnecke and George Timson's original diagram.|
VISTA is not modular in the sense of being a structure built by snapping together packages like Legos, which is why projects designed around updating or replacing those Legos invariably fail. A VISTA package is not a Lego.
Instead, VISTA is modular in the sense of being a complex architecture of extensible frameworks, each of which has different kinds of Legos that can be plugged into it. A VISTA package is a collection of different kinds of Legos, each of which is plugged into its appropriate framework to activate it.
The core architecture of VISTA, then, can only be understood by understanding what these extensible frameworks are and how they work together to accomplish the system's functions. The components of all of VISTA's user-oriented packages (like Lab, Pharmacy, Scheduling, and so on) are extensions of those frameworks rather than separable "pieces" of the system.
For example, the Lab package doesn't automate a hospital's Lab department. Instead, it adds numerous plug-in components to VISTA's extensible frameworks until *they* can automate a hospital's Lab department. In other words, VISTA Lab is not a separable program like a word processor that does Lab things. It is in a sense data that the core VISTA architecture uses to know how to do Lab things.
So long as people plan VISTA projects assuming the widespread but naive model of packages as Legos, their projects will fail, often at great expense. Understanding VISTA's unusual form of modularity and how its architecture is built from it is the first step toward being able to carry out successful VISTA projects.
This first webinar in our series on VISTA fundamentals introduces these ideas. You can watch it at the vxJourney VISTA Webinars site here: https://www.vxvista.org/display/vx4Learn/Introduction+to+VISTA+Architecture
My thanks to Fabian Lopez for creating the vxJourney VISTA Webinars series and encouraging me to create and deliver this presentation.