ALTO (Analyzed Layout and Text Object) is a XML Schema that details technical metadata for describing the layout and content of physical text resources, such as pages of a book or a newspaper. It most commonly serves as an extension schema used within the Metadata Encoding and Transmission Schema (METS) administrative metadata section. However, ALTO instances can also exist as a standalone document used independently of METS.
hOCR is a format for representing OCR output, including layout information, character confidences, bounding boxes, and style information. It embeds this information invisibly in standard HTML. By building on standard HTML, it automatically inherits well-defined support for most scripts, languages, and common layout options. Furthermore, unlike previous OCR formats, the recognized text and OCR-related information co-exist in the same file and survives editing and manipulation. hOCR markup is independent of the presentation.