code: SubjectScheme getSubjectScheme(final Element root) {
          subjectSchemeReader.reset();
          logger.debug("Loading subject schemes");
          final List<Element> subjectSchemes = toList(root.getElementsByTagName("*"));
          subjectSchemes.stream()
                  .filter(SUBJECTSCHEME_ENUMERATIONDEF::matches)
                  .forEach(enumerationDef -> {
                      final Element schemeRoot = ancestors(enumerationDef)
                              .filter(SUBMAP::matches)
                              .findFirst()
                              .orElse(root);
                      subjectSchemeReader.processEnumerationDef(schemeRoot, enumerationDef);
                  });
          return subjectSchemeReader.getSubjectSchemeMap();
      }
docs: Read subject scheme definitions.