Lesson RefId xml:lang SourceObjects SourceObject SIF_RefObject CurriculumStructures CurriculumStructureRefId SubjectArea Title Duration Units Description Procedure Strategies Strategy LearningObjectives LearningObjective SupportingActivities ActivityRefId LearningStandards LearningStandardItemRefId LearningResources LearningResourceRefId LessonSources LessonSource Author Name Organization Address Email SIF_Metadata SIF_ExtendedElements