Structure of ALTO Files

An ALTO file consists of three major sections as children of the root <alto> element:

• <Description>
• <Styles>
• <Layout>

The <Description> section contains metadata about the ALTO file itself and processing information on how the file was created.

The <Styles> section contains the text and paragraph styles with their individual descriptions:

• <TextStyle> has font descriptions
• <ParagraphStyle> has paragraph descriptions, e.g. alignment information

The <Layout> section contains the content information. It is subdivided into <Page> elements.

A page consists of margins and printspace, all of those are non-intersection rectangular areas within the page area. Each of these can contain any number of objects like lines, images or textblocks and more. A textblock is divided into textlines and those are divided furthermore in strings and spaces.

The global structure of the ALTO file is as follows:

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.