I find the analogy that I use most frequently is comparing the data model to a blueprint. Most non-technical friends, family, and neighbors understand this analogy. “Just like you need a blueprint to ensure a sound building structure, you need a data model to ensure a sound application.” Sometimes I also explain to people that a data model is nothing more than a fancy spreadsheet that contains not just the spreadsheet columns, but also the business rules binding these columns. If both the blueprint and spreadsheet analogies fail, I quickly change the subject to the other person and ask what they do (and hope that they never ask me again!).