4. The method of claim 3 , further comprising performing by the first thread: retrieving one or more error checking results from the second queue; and for each retrieved error checking result: determining whether an element currently exists within the document that has an ID that is the same as the ID associated with the retrieved error checking result; and in response to determining that the element currently exists within the document that has the ID that is the same as the ID associated with the retrieved error checking result, generating an indication that the element is in error.
6. The method of claim 4 , further comprising performing by the first thread: storing 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 determining whether the element currently exists within the document that has the ID that is the same as the ID associated with the retrieved error checking result comprises determining whether the element is stored within the data structure that has the ID that is the same as the ID associated with the retrieved error checking result.