An application can use native field structures, which can store information such as "Creation Date of the Document", "Formula", a specially formatted number, a reference to text in another part of the document. Fields are commonly used for document automation, so that the application itself can include certain information among the contents of the document, with possibly no extra user intervention required. Thus a way can be provided to save this field definition information in a markup language (ML) document without data loss. When the format is stored in a markup language, other applications can validate the document stored in accordance with the native format. The other applications can represent the information in accordance to the degree to which they are aware of the unique properties of the application used to generate the document.