I wouldn't do a separate section for the OCR engine specific elements. I think it is much better to discuss them in their context. You could move the general remarks up somewhere and create a section with ocr_column, ocr_carea, ocrx_block and another one with ocr_line and ocrx_line and finally move the ocrx_word up a little.
https://github.com/kba/hocr-spec/pull/84#issuecomment-256556599:
I wouldn't do a separate section for the OCR engine specific elements. I think it is much better to discuss them in their context. You could move the general remarks up somewhere and create a section with
ocr_column,ocr_carea,ocrx_blockand another one withocr_lineandocrx_lineand finally move theocrx_wordup a little.