If you want to access data as a relational database, then the data needs to be arranged into records which contain a set number of fields each of which contains a single value. That is the basis of the "rigidity" of
's XML format. The sample that you show does not appear to be divided into records (unless you are omitting some enclosing tag or unless you have one record per file) and some of the fields you show (e.g. PotentialSpecificHeat) contain multiple values. You need to conceptually reduce your data to fields, records, and values before you can treat it like a database regardless of whether you use AnyData or something else. If you can tell us how you'd do that reduction perhaps we can make some suggestions.