Method for automatically migrating power builder application to an open architecture is disclosed. The method includes converting to ASCII character format stream, parsing the stream to form constructs, generating a model from the constructs, analyzing the model and building trees in the model in the power builder format. The apparatus of the invention includes a schema of trees, one set, representing trees in the power builder format and another set in the selected open architecture format and a set of mappings defining correspondence between the two sets. Trees in one set are transformed into the other and attached in the model. An Unparser is provided having a class generator which generates classes including a global variable class in the open architecture and the classes are filled with the help of the parser and a model traverser by querying and responses thereto.