I keep harping on about this at work - a sqlite file carries its schema with it so you can inspect it. With foreign keys, notnull, check and other constraints you can easily make out what the data is about. There is a driver in every language it seems, and if not the docs are very good so if you are handy with FFI it is easy to build one. It can be far more compact than XML (gulp! SOAP) with the equivalent amount of data as the amount of data gets larger. Being a single file, it can be sent over the wire like any other. And you use SQL to interface with it.
Currently building software for the ATO (Single Touch Payroll) which uses SBR (https://en.wikipedia.org/wiki/Standard_Business_Reporting). The SBR project is listed as having on-going problems, and has cost the ATO ~$AUD1b to date (https://en.wikipedia.org/wiki/List_of_failed_and_overbudget_...). One of the reasons cited is that it uses XBRL (https://en.wikipedia.org/wiki/XBRL). Now imagine if it used sqlite...