What is a IDML File Type?
IDML packages contain a hierarchy of XML files and directories. The root directory of the archive contains a designmap.xml file, which specifies high-level document properties, as well as the document layout. The archive also contains the following folders, which are used to store parts of the document:
Resources: Contains document elements, such as colors, fonts, and paragraph styles; includes Graphics.xml, Fonts.xml, Styles.xml, and Preferences.xml.
Spreads: Stores document spreads.
Stories: Contains all document stories.
XML: Stores document elements and settings; includes BackingStory.xml, Tags.xml, and Mapping.xml.
MasterSpreads: Contains MaterSpreads.xml, which specifies all master spreads displayed on document pages, such as rectangles, ellipses, groups, polygons, buttons, and text frames.
META-INF: Stores the standard container.xml file for UCF packages.
IDML files were designed to replace .INX files, which are more difficult to create and edit. IDML files provide an interchangeable format for Adobe InDesign documents, as well as a way for third-party tools to modify and assemble InDesign documents.
The InDesign CS4 tag language has been introduced. InDesign supports always back compatibility with INX files.