Ralph Johnson and Tom Munnecke discussing refactoring of VistA
Channel: Tom Munnecke
Date: 16/12/2011

I had a video chat with Ralph Johnson, software refactoring and object-oriented patterns guru, regarding ways of looking at refactoring VistA. He talks about "Big Ball of Mud" systems http://www.laputan.org/mud/ , and ways of managing them, particularly through Shearing Layers http://wirfs-brock.com/blog/2011/08/26/agile-architecture-myths-4-because-you... which were the topic of Stewart Brand's "How Buildings Learn" book. I talked about VistA patterns of "Creating a Path of Least Resistance" - with the example that the 1978 VistA design meeting created a common date management routine that was Y2K compatible, making it easier to by compatible. 

I also spoke about the notion of creating a "Shearing Layer" above VistA - a semantic overlay connecting the existing VistA system data dictionary to the outside world, allowing VistA to participate in the Linked Data world, RDF Semantic mashups. This would also have the advantage of extending the current VistA privacy semantics out to the network interface. 

I also talked about the scale of VIstA being a critical factor that is often overlooked - "bigger is different" and this has both its drawbacks and its advantages.