17. The system of claim 12 , wherein the error checker is configured to apply error checking to a retrieved copy of a new element responsive to determining that an element currently exists within the document that has an ID that is the same as the ID associated with the retrieved copy of the new element.
17. The system of claim 12 , wherein the error checker is configured to apply error checking to a retrieved copy of a new element responsive to determining that an element currently exists within the document that has an ID that is the same as the ID associated with the retrieved copy of the new element. 18. The system of claim 17 , wherein the parser is further configured to store each new element in a data structure that stores a plurality of elements that currently exist in the document and an ID associated with each of the plurality of elements; and wherein the error checker is configured to apply error checking to a retrieved copy of a new element responsive to determining that the element is stored within the data structure that has the ID that is the same as the ID associated with the retrieved copy of the new element.