A system can generate an expression tree hierarchy based on a database query that refers to dynamic data of a database having a data model. The dynamic data is undefined in the data model of the database. The system can invoke a process that traverses the expression tree hierarchy to transform the expression tree hierarchy and iteratively or recursively translate multiple expression fragments of the expression tree hierarchy in accordance with the process while maintaining a contextual type stack. A particular iteration or recursion operates on a particular expression fragment of the multiple expression fragments to convert the particular expression fragment into another expression fragment for another expression tree hierarchy.