I love the example that this provides with respect to the conflation of "Storage" with "FileSystem", while data may indeed be stored on a filesystem somewhere,

I love the example that this provides with respect to the conflation of "Storage" with "FileSystem", while data may indeed be stored on a filesystem somewhere, the habitual thinking that appends " to file" to the phrase "I need to save these data" seems unintentionally limiting to me. Instead of trying to answer questions like "what should our file format look like?" It seems more interesting and valuable to ask first, "what storage is most appropriate", the answer may be REST, database, file, /dev/null, or any abstraction over one or more of these. You may then find that questions about file format, or structure simply disappear, it is the role of the storage mechanism chosen to efficently store and recover the data, use the hard work that the team that built that solution invested, and apply your own hard work to solving your own problems. With cloud and mobile being added to the set of common target platforms (however ill-defined), I hear/read people asking "how do I read/write a file" increasingly often, when on those platforms (and many other) the concept of a file (at the application layer) may not be useful at all...