The structured-content layer

The tagged-XML layer is a short vocabulary: XMLTag names a tag, XMLElement applies it, and an XmlStory holds the tree.

In short XML/Tags.xml lists the document's tags, one XMLTag each, with a Name and a typed TagColor property. XML/BackingStory.xml holds one XmlStory, which is shaped like an ordinary story: paragraph and character ranges with XMLElement nodes among the Content. Each XMLElement names its tag in MarkupTag. Nodes for XML attributes, comments and processing instructions, and the tag-to-style maps, exist in the vocabulary but are rare: none of the 305 documents in the census uses them.

XMLTag: the tag names (Tags.xml)

XML/Tags.xml has an idPkg:Tags root with one XMLTag per tag the document defines. A tag is a name and a colour; it holds no content. Other parts refer to it by Self, which InDesign writes as XMLTag/<name>. The colour shown beside the tag in InDesign is a typed property, <Properties><TagColor type="enumeration">LightBlue</TagColor></Properties>.

Every InDesign document defines at least the tag Root.

Attribute · XMLTag	Values	Paged	paged.set
Name	enum	not read
Self	XMLTag reference	not read
TagColor in Properties	—	not read

XmlStory: the backing story (BackingStory.xml)

XML/BackingStory.xml has an idPkg:BackingStory root holding a single XmlStory. Note the spelling: XmlStory, not XMLStory. It is built like a layout story, with the same story attributes (AppliedTOCStyle, TrackChanges, StoryTitle, UserText) and the same body of ParagraphStyleRange and CharacterStyleRange elements. It anchors the root of the XML tree and holds content that has been tagged but not placed on a page.

In an untagged InDesign document the backing story is one paragraph whose character range holds a few zero-width U+FEFF characters around the root element: <XMLElement Self="di3" MarkupTag="XMLTag/Root"/>.

XMLElement: the tree

An XMLElement applies a tag. MarkupTag names the XMLTag, and Self is its id. Nesting one XMLElement inside another builds the hierarchy. An element can sit in a character range among the text it tags, or carry an XMLContent attribute naming the Self of placed content, such as a story or a frame, that it labels.

Attribute · XMLElement	Values	Paged	paged.set
MarkupTag	XMLTag reference	not read
Self	text	not read

In the census, 271 documents carry an XMLElement, almost always the single root element; two nest elements inside it, and XMLContent does not occur at all.

The rarer nodes

The vocabulary has a few more node types for a tagged tree. None of them appears in the census, so their attributes are listed by name only:

The maps (Mapping.xml)

XML/Mapping.xml holds the mappings between tags and styles in both directions: XMLExportMap maps a style to a tag, and XMLImportMap a tag to a style, each naming an XMLTag in MarkupTag and a paragraph or character style in MappedStyle. InDesign did not write this part in any of the census documents, and the design map has no reference to it; it appears only in generated files, as an empty idPkg:Mapping root.

In Paged: none of these elements is read; the layout is the same with or without them. The XML parts are copied byte for byte when a document is saved. See reading and preserving tagged XML.

Planned

Frequently asked questions

What is the difference between an XMLTag and an XMLElement? An XMLTag in Tags.xml is a name in the document's tag list. An XMLElement in the backing story applies that tag to content, naming it in MarkupTag. Many elements can use one tag.

Is it XmlStory or XMLStory? XmlStory, with only the X capitalised, unlike XMLTag and XMLElement.

What does an untagged document's backing story contain? One paragraph with a single XMLElement applying the Root tag, surrounded by a few zero-width U+FEFF characters.

Does InDesign write XML/Mapping.xml? Not in any of the InDesign-exported documents in the census. The design map does not reference it.