Strategies for Replacing Systems in Agile Projects

In replacement projects one of the biggest questions is what strategy to use in replacing the old system. The simplest strategy is to wait until the new system is ldquoat least as good as the old onerdquo before switching. Although this strategy sounds compelling it has many serious drawbacks. An alternative strategy is based on what I call a ldquominimal deployable entityrdquo. Switch systems when you have just enough to be able to survive with the new system. The concept is similar to ldquominimal marketable featurerdquo but more focused on deployment strategy. This paper uses two projects as concrete examples of patterns and principles that can be used to define a strategy for a minimal deployable entity.