• Preserve an ordinary EPUB rather than a proprietary interactive package. • Preserve semantic structure alongside human-readable fallback. • Inspect metadata without executing application code. • Know which representation is authoritative. • Preserve 3D assets with poster, scale, orientation, and provenance. • Distinguish work, publication, artifact, and element identity. • Preserve the publication independently of mutable reader annotations. • Preserve machine-readable bibliography alongside visible references. • Validate cross-file relationships. • Retain useful semantics after the original software becomes obsolete.