USPTO Patent XML, understanding the us-field-of-classification-search element

Question

I'm working with XML from the USPTO bulk download which provides weekly downloads of XML of published patent grants. I'm using this documentation to understand the files.

I'm having trouble understanding the significance of the us-field-of-classification-search element (see page 26 in the referenced documentation). It seems to be repeating fields that have already been provided, specifically, it seems to be repeating classification information provided by other elements such as those beginning on page 11 of the aforementioned documentation.

What is this element actually providing?

Answer 1

Page 83 of the referenced documentation is helpful:

The us-field-of-classification-search element will always be present. If the examiner did do a classification search, the element will contain one or more classification-national records and/or one us-classifications-ipcr record. If the examiner did not do a classification search, the element will contain a single classification-national record in which the content of the main-classification will be "None."

A classification search will provide national and international classes to retrieve prior art, these classes being stored as us-classifications-ipcr and classification-national.

Since the classification of an application is checked at allowance, at least a class found during that search will be used to classify the granted application, thus at least one value of the element us-field-of-classification-search is repeated as official classe of the grant.