To keep building on this, I think the word "parsing" is just the tip of the iceberg. Parsing is one way to port data across a type boundary, where the source an

To keep building on this, I think the word "parsing" is just the tip of the iceberg. Parsing is one way to port data across a type boundary, where the source and dest types are optimized for different use cases (e.g. serialization vs type-safe representation). Since the semantic Venn diagrams of any two types might have areas of non-overlap, parse-don't-validate means establishing clear boundaries in your program where those translations happen, then defining the types on either side of the boundary to rule out the possibility of nonsense states elsewhere throughout the program. The idea of nonsense states is closely related and discussed more here[0] and here[1]. [0] http://blog.jenkster.com/2016/06/how-elm-slays-a-ui-antipattern.html http://blog.jenkster.com/2016/06/how-elm-slays-a-ui-antipatt... [1] https://kentcdodds.com/blog/make-impossible-states-impossible https://kentcdodds.com/blog/make-impossible-states-impossibl...