The companion formats

The companion formats are four standalone XML files that reuse IDML's vocabulary but are not packages.

In short: Four file kinds borrow IDML's element vocabulary outside the package: InDesign Snippets (.idms), libraries, story-only / InCopy files (.icml), and assignment files (.icma). Each is a single, standalone XML file rather than a ZIP archive, and most announce themselves with an aid processing instruction at the top. This reference page states each one as a fact — its name and extension, the marker that identifies it, what it carries, and the precise way it differs from a full .idml package. None of them is something Paged can open.

Four file kinds reuse IDML's element vocabulary outside the package. This page states each as a fact: its name and extension, the marker that identifies it, what it carries, and the precise way it differs from a full .idml package. None is something Paged can open.

Not yet parsedevery format on this page

The shared shape: standalone XML, not a package

A full IDML document is a ZIP archive — a mimetype entry, a designmap.xml root, and the parts the design map references. Every format below is the opposite: a single, standalone XML file with no archive wrapper and no design map. That one difference is what each "how it differs" row reduces to, and it is why none of them reaches Paged's reader.

Three of these files announce themselves with a processing instruction at the top — an aid instruction whose attribute and value identify the kind. They are facts of the format, listed here so you can identify a file by inspection.

InDesign Snippets (.idms)

A snippet is the elements of a single page captured into one XML file: the page items plus whatever styles, colors, and layers are needed to re-create and format them when the snippet is later placed into a document. It uses the same element names you find inside a package — Spread and Story for the items and their text, ParagraphStyle, CharacterStyle, and Color for the formatting those items depend on.

How it differs from a package: a snippet is a fragment, not a document. It carries no designmap.xml, so nothing names a root or enumerates the document's stories; it is not a ZIP archive, so there is no mimetype to confirm. Its meaning is completed at placement time by the host document, which reconciles incoming names against what already exists (a Color of the same name already in the document wins over the one in the snippet, for instance). A renderer cannot resolve a fragment in isolation.

Not yet parsed.idms

Libraries

A library is a collection of reusable items. The items themselves are InDesign snippets — so each entry carries the same SnippetType="PageItem" marker and the same fragment content as a standalone .idms file.

How it differs from a package: a library is a container of fragments, not a document, and each fragment is subject to the same placement-time resolution as any snippet. There is no design map and no single document to render.

Not yet parsedlibrary items (snippets)

Story-only / InCopy files (.icml)

An ICML file holds one story — the text content and its formatting — with no page or spread geometry around it. It is the unit InDesign and InCopy exchange when an editor works on copy independently of layout. It is marked by the SnippetType="InCopyInterchange" instruction.

How it differs from a package: it is text without a place to sit. A package's stories are reached through the design map's StoryList and laid into frames on spreads; an ICML file has neither a design map nor a spread, so there is no frame, no geometry, and no document identity. Paged builds a rendered document from frames on pages, and an ICML file supplies none of that scaffolding.

Not yet parsed.icml

Assignment files (.icma)

An assignment file is InCopy's editorial bookkeeping: it records which stories are checked out to which editor as a unit of work. It is marked by the type="assignment" instruction rather than a SnippetType.

How it differs from a package: it is workflow metadata, not content. It references stories rather than containing a renderable document, and like the others it is a standalone XML file with no design map and no archive wrapper. There is nothing here for a renderer to draw.

Not yet parsed.icma

Side by side

Why each companion format is unsupported, and what supporting it would require, is the subject of when each applies.

Frequently asked questions

What is the difference between an .idms snippet and an .icml story file? An .idms snippet captures the page items of a single page plus the styles, colors, and layers needed to re-create their formatting when placed into a document; it is marked <?aid SnippetType="PageItem"?>. An .icml story-only / InCopy file carries one story's text and formatting with no page or spread geometry around it, and is marked <?aid SnippetType="InCopyInterchange"?>. One is a layout fragment, the other is text with no place to sit.

How can I tell which companion format a standalone XML file is? Three of the four announce themselves with a processing instruction at the top of the file: <?aid SnippetType="PageItem"?> marks a snippet (and a library item), <?aid SnippetType="InCopyInterchange"?> marks an ICML story file, and <?aid type="assignment"?> marks an assignment file. These markers are facts of the format, so you can identify a file by inspection.

Can Paged open any of these companion formats? No. Every format on this page is a standalone XML file with no ZIP archive wrapper and no designmap.xml root, which is exactly the shape Paged's reader cannot enter — so all of them carry a not-yet-parsed status. The one form Paged does open is the full IDML package: a ZIP archive with a mimetype, a design map, and the parts the design map references.