Question: when did the claim to the caliphate become central to ottoman ideology
[{'answer': '1517', 'provenance': [{'wikipedia_id': '804036', 'title': 'Caliphate', 'start_paragraph_id': 2, 'start_character': 192, 'end_paragraph_id': 2, 'end_character': 196, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '804036', 'title': 'Caliphate', 'start_paragraph_id': 58, 'start_character': 0, 'end_paragraph_id': 58, 'end_character': 1221, 'bleu_score': 0.990171692033262, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 12004212693893032281}, 'section': 'Section::::Ottoman Caliphate (1517–1924).\n'}]}]