A method and system for modifying program applications of a legacy computer system to directly output data in XML format models the legacy computer system, maps the model to an XML schema and automatically modifies one or more applications to directly output XML formatted data in cooperation with a writer engine and a context table. A modeling engine lists the incidents within the applications that write data and generates a report data model. The report data model includes statically determined value or type of the data fields and is written in a formal grammar that describes how the write operations are combined. A modification specification is created to define modifications to the legacy computer system applications that relate applications that write data to the XML schema. A code generation engine then applies the modification specification to the applications to write modified applications that, in cooperation with a writer engine and context table, directly output XML formatted data from the legacy computer system without a need for transforming the data.