14. A computer readable medium comprising machine readable instructions that, when executed by a computer, perform a method that uses a structured markup language document having a syntax described by a schema, the structured markup language document also having a plurality of data entry fields each corresponding to an markup language node, wherein the markup language nodes are arranged in a hierarchical structure of parent nodes having child nodes, and wherein the hierarchical position of each said markup language node in the hierarchical structure is expressed as a corresponding fragment of the markup language, the method comprising: displaying an electronic form on a UI for interactive data entry, wherein: the electronic form has a plurality of data entry fields respectively corresponding to data entry fields of the structured markup language document; and the electronic form is associated with a electronic form definition document defining for each said parent node a maximal information fragment to encode each editable fragment of the parent node, the maximal information fragment for each said parent node having a plurality of portions each corresponding to the fragment of a respective said child node of the parent node, wherein: the electronic form definition document encodes schema information from the schema to achieve schema awareness at edit time; two said portions correspond to the longest and the shortest said fragments of respective said child nodes; and the maximal information fragment is smaller than a combination of all possible fragments of the child nodes of the parent node; for each said parent node, using the form definition document having the maximal information fragment and the schema information at edit time to determine for each data entry field a corresponding said portion of the maximal information fragment to perform data entry for the data entry field, such that data entry for each said data entry field is valid with respect to the schema.
14. A computer readable medium comprising machine readable instructions that, when executed by a computer, perform a method that uses a structured markup language document having a syntax described by a schema, the structured markup language document also having a plurality of data entry fields each corresponding to an markup language node, wherein the markup language nodes are arranged in a hierarchical structure of parent nodes having child nodes, and wherein the hierarchical position of each said markup language node in the hierarchical structure is expressed as a corresponding fragment of the markup language, the method comprising: displaying an electronic form on a UI for interactive data entry, wherein: the electronic form has a plurality of data entry fields respectively corresponding to data entry fields of the structured markup language document; and the electronic form is associated with a electronic form definition document defining for each said parent node a maximal information fragment to encode each editable fragment of the parent node, the maximal information fragment for each said parent node having a plurality of portions each corresponding to the fragment of a respective said child node of the parent node, wherein: the electronic form definition document encodes schema information from the schema to achieve schema awareness at edit time; two said portions correspond to the longest and the shortest said fragments of respective said child nodes; and the maximal information fragment is smaller than a combination of all possible fragments of the child nodes of the parent node; for each said parent node, using the form definition document having the maximal information fragment and the schema information at edit time to determine for each data entry field a corresponding said portion of the maximal information fragment to perform data entry for the data entry field, such that data entry for each said data entry field is valid with respect to the schema. 16. The computer readable medium as defined in claim 14 , wherein: the method further comprises entering the data from the data entry into a structured markup language file that corresponds to the structured markup language document; and each said data entry field has a corresponding field in the structured markup language file.