code: protected String readSchemaDefinition(String schemaUri) throws CmsRuntimeException {
  
          // the schema definition is located in a separate file for easier editing
          String schemaDefinition;
          try {
              schemaDefinition = CmsFileUtil.readFile(schemaUri, CmsEncoder.ENCODING_UTF_8);
          } catch (Exception e) {
              throw new CmsRuntimeException(
                  Messages.get().container(Messages.ERR_XMLCONTENT_LOAD_SCHEMA_1, schemaUri),
                  e);
          }
          return schemaDefinition;
      }
docs: Convenience method to loads the XML schema definition for this value type from an external file.<p>
  
  @param schemaUri the schema uri to load the XML schema file from
  
  @return the loaded XML schema
  
  @throws CmsRuntimeException if something goes wrong