1. A system comprising: a user interface (UI) rule control, wherein the UI rule control is a re-usable control; a parser module; a display; a memory storing processor-executable process steps; and a parser processor coupled to the memory, and in communication with the parser module and the UI rule control and operative to execute the processor-executable steps to cause the system to: provide, by the UI rule control, a user interface to a user via the display, the user interface including one or more data-entry fields; receive an expression in the one or more data-entry fields; transform, via the parser module, the expression into Abstract Syntax Tree (AST), wherein the AST is usable by two or more different types of runtime engines to provide a response to the received expression; and output, via the UI rule control, the AST, wherein the AST is usable by two or more different types of runtime engines to compile one or more rules, authored via a logic of the UI rule control, based on a runtime environment of the runtime engine.