Patent ID: 8196135

Claim:
A method of recordal of changes to a markup language file having a document type definition (DTD) or XML (Extensible Markup Language) Schema, wherein the method comprises the following steps: creating a delta file; assigning to the delta file a document type definition (DTD) or XML Schema which defines element types corresponding to the element types of the document type definition (DTD) or XML Schema of the markup language file, the element types of the delta file having the same constraints on the type, number and order of the document type definition elements or the XML Schema element types as the constraints defined in the document type definition (DTD) or XML Schema of said markup language file; and recording in the delta file either: i) only changes to the contents of said markup language file such that element instances not changed in the markup language file are not recorded in the delta file, or ii) all the data of the markup language file and the changes to the markup language file, in each case the changes recorded in the delta file being validated against a document type definition (DTD) or XML Schema which is substantially the same as the document type definition (DTD) or XML Schema of said markup language file.