3. The method of claim 2 wherein the index information in the vIndex key associated with the first vNode includes at least one of the start date and the end date.
3. The method of claim 2 wherein the index information in the vIndex key associated with the first vNode includes at least one of the start date and the end date. 4. The method of claim 3 wherein when the vNode exists in a head version of the structured document, the index information in the vIndex key associated with the first vNode includes an end date set to a value to indicate it is undetermined.