The Metadata Object Description Schema (MODS) is a hierarchical XML-based bibliographic description schema created by the Library of Congress’ Network Development and MARC Standards Office. MODS is meant to be a compromise between the complex MARC system and the simplistic Dublin Core metadata.
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XML Path Language (XPath) is a query language employed by the XML forms in the repository to both write the proper nodes to the MODS XML datastream and read the nodes from that datastream t to display in the form.
How XPath Syntax and XML match up (color coded):
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XPath Syntax noted in metadata mapping sheets and employed in XML forms
mods:titleInfo[@lang="eng" @displayLabel="Title (English)"]/mods:title
Resulting XML in MODS datastream
<mods xmlns="http://www.loc.gov/mods/v3" xmlns:mods="http://www.loc.gov/mods/v3" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xlink="http://www.w3.org/1999/xlink">
<titleInfo lang="eng" displayLabel="Title (English)">
<title>Test Collection</title>
</titleInfo>