Item A: PDF files after format conversion can be divided into browse-level PDF and print-level PDF according to image quality, and browse-level PDF can be used as finished materials in e-book products; Item b, the structured processing of digital content books is carried out on PDF files, and the processing goal is consistent with the structured processing of paper books; Item d is different from the finished data of paper books. The data processed by digital content books include: single-layer vector PDF file, book metadata XML file, structured XML file and book ePub file.