1. A method in a data processing system for generating a schema definition from a nested data structure definition defined in a legacy computer language, comprising: identifying a plurality of identified data structures by scanning a source code stored in a computer-readable storage medium, wherein the source code is written in a legacy computer language; selecting via a Graphical User Interface (GUI) a nested data structure from the plurality of identified data structures; receiving a language-specific metamodel generated from the nested data structure definition written in the legacy computer language; naming and defining a first complex type schema element for the nested data structure, wherein naming and defining comprises setting a content model of the first complex type schema element to sequence; and creating the schema definition by walking through the language-specific metamodel to examine each node in a plurality of nodes of the language-specific metamodel, and for each node, creating a respective schema element according to a predefined mapped relationship, wherein creating the schema definition further comprises populating a schema tree; and serializing the schema tree after it is populated.