Data is sharply shape-constrained while documents aren't. You can easily look at data and devise traversal schemes to get at the information you want, whereas w

Data is sharply shape-constrained while documents aren't. You can easily look at data and devise traversal schemes to get at the information you want, whereas with documents, this isn't nearly as easy. If you're ingesting XML into a database, it's often easier to just put the whole XML in as a text field, whereas with JSON data, you can just extract the fields you want and insert them in.