1. A method of expressing a change history for a markup language document comprising: identifying a source markup language document and at least one modification to the source markup language document; creating at least one delta document specifying the modification to the source markup language document, wherein the delta document is independent of the source markup language document and is coded in a different language than the source markup language document, wherein creating the delta document comprises specifying each modification to the source markup language document, within the delta document, as an “add” operation or a “remove” operation comprising a reference to a location in the source markup language document to which each respective modification is to be applied and including, within each “add” operation and “remove” operation, a time stamp indicating when the modification was implemented; and storing, within a data storage device, the source markup language document and the delta document.