Checks Reference

Horn covers every failure condition of the Matterhorn Protocol 1.1 for PDF/UA-1 (ISO 14289-1). The protocol's tables list 137 index entries (its introduction still says 136; version 1.1 added 13-008):

	Conditions	Coverage
Machine-checkable (M)	87	87/87 implemented as automated checks
Human judgment (H)	48	48/48 reported as manual review items when applicable
No test defined	2	23-001 and 27-001 are reported as not applicable
Total	137	137/137 appear in every report

Every result's rule_id is the official Matterhorn index (e.g. 28-010 — a Widget annotation not nested in a <Form> tag), so findings can be compared directly with PAC, veraPDF and the protocol itself. Checks that go beyond the protocol use extension ids of the form NN-xNN (listed at the end).

Run horn coverage (or horn coverage --json) to print this matrix from the binary you have installed.

PDF/UA-2 (ISO 14289-2:2024) documents — pdfuaid:part 2 — get the same checks (adapted where PDF 2.0 changes the rules) plus the PDF/UA-2 rules for the requirements that only exist in PDF/UA-2.

Outcomes and severities

Outcome	Meaning
Pass	The document satisfies this condition
Fail	A violation was found (includes a message and, where known, a page/element)
NeedsReview	The condition requires human judgment; the document contains the relevant feature (tables, figures, JavaScript, …). Listed in text output with --review.
NotApplicable	The condition does not apply to this document

Severities: error (PDF/UA-1 requirement violated), warning (potential issue or heuristic), info (informational). --fail-on selects which severities affect the exit code; NeedsReview never does.

Matterhorn Protocol coverage

Legend — How: M machine-checkable, H human judgment. Module: the check module in src/checks/ that emits the id.

Checkpoint 01: Real content tagged

Rule	How	Failure condition	Module
01-001	H	Artifact is tagged as real content.	human_review
01-002	H	Real content is marked as artifact.	human_review
01-003	M	Content marked as Artifact is present inside tagged content.	content_stream
01-004	M	Tagged content is present inside content marked as Artifact.	content_stream
01-005	M	Content is neither marked as Artifact nor tagged as real content.	baseline, content_stream
01-006	H	The structure type and attributes of a structure element are not semantically appropriate for the content.	human_review
01-007	M	Suspects entry has a value of true.	dict_entries

Checkpoint 02: Role Mapping

Rule	How	Failure condition	Module
02-001	M	One or more non-standard tag's mapping does not terminate with a standard type.	baseline, dict_entries, structure
02-002	H	The mapping of one or more non-standard types is semantically inappropriate.	human_review
02-003	M	A circular mapping exists.	structure
02-004	M	One or more standard types are remapped.	structure

Checkpoint 03: Flickering

Rule	How	Failure condition	Module
03-001	H	One or more Actions lead to flickering.	human_review
03-002	H	One or more multimedia objects contain flickering content.	human_review
03-003	H	One or more JavaScript actions lead to flickering.	human_review

Checkpoint 04: Color and Contrast

Rule	How	Failure condition	Module
04-001	H	Information is conveyed by contrast, color, format or layout but the content is not tagged to reflect that meaning.	human_review

Checkpoint 05: Sound

Rule	How	Failure condition	Module
05-001	H	Media annotation present, but audio content not available in another form.	human_review
05-002	H	Audio annotation present, but content not available in another form.	human_review
05-003	H	JavaScript uses beep function but does not provide another means of notification.	human_review

Checkpoint 06: Metadata

Rule	How	Failure condition	Module
06-001	M	Document does not contain an XMP metadata stream.	version
06-002	M	The XMP metadata stream in the Catalog dictionary does not include the PDF/UA identifier.	baseline, metadata, version
06-003	M	XMP metadata stream does not contain dc:title.	baseline, metadata
06-004	H	dc:title does not clearly identify the document.	human_review

Checkpoint 07: Dictionary

Rule	How	Failure condition	Module
07-001	M	ViewerPreferences dictionary of the Catalog dictionary does not contain a DisplayDocTitle entry.	baseline, metadata
07-002	M	ViewerPreferences dictionary of the Catalog dictionary contains a DisplayDocTitle entry with a value of false.	metadata

Checkpoint 08: OCR Validation

Rule	How	Failure condition	Module
08-001	H	OCR-generated text contains significant errors.	human_review
08-002	H	OCR-generated text is not tagged.	human_review

Checkpoint 09: Appropriate Tags

Rule	How	Failure condition	Module
09-001	H	Tags are not in logical reading order.	human_review
09-002	H	Structure elements are nested in a semantically inappropriate manner. (e.g., a table inside a heading).	human_review
09-003	H	The structure type (after role mapping) of a structure element is not semantically appropriate.	human_review
09-004	M	A table-related structure element is used in a way that does not conform to the syntax defined in ISO 32000-1, Table 337.	baseline, nesting, tables
09-005	M	A list-related structure element is used in a way that does not conform to Table 336 in ISO 32000-1.	baseline, lists, nesting
09-006	M	A TOC-related structure element is used in a way that does not conform to Table 333 in ISO 32000-1.	nesting
09-007	M	A Ruby-related structure element is used in a way that does not conform to Table 338 in ISO 32000-1.	nesting
09-008	M	A Warichu-related structure element is used in a way that does not conform to Table 338 in ISO 32000-1.	nesting

Checkpoint 10: Character Mappings

Rule	How	Failure condition	Module
10-001	M	Character code cannot be mapped to Unicode.	font_program

Checkpoint 11: Declared Natural Language

Rule	How	Failure condition	Module
11-001	M	Natural language for text in page content cannot be determined.	baseline, language, metadata
11-002	M	Natural language for text in Alt, ActualText and E attributes cannot be determined.	language
11-003	M	Natural language in the Outline entries cannot be determined.	language
11-004	M	Natural language in the Contents entry for annotations cannot be determined.	language
11-005	M	Natural language in the TU entry for form fields cannot be determined.	language
11-006	M	Natural language for document metadata cannot be determined.	language
11-007	H	Natural language is not appropriate.	human_review

Checkpoint 12: Stretchable Characters

Rule	How	Failure condition	Module
12-001	H	Stretched characters are not represented appropriately.	human_review

Checkpoint 13: Graphics

Rule	How	Failure condition	Module
13-001	H	Graphics objects other than text objects and artifacts are not tagged with a <Figure> tag.	human_review
13-002	H	A link with a meaningful background does not include alternative text describing both the link and the graphic's purpose.	human_review
13-003	H	A caption is not tagged with a <Caption> tag.	human_review
13-004	M	<Figure> tag alternative or replacement text missing.	baseline, images
13-005	H	ActualText used for a <Figure> for which alternative text is more appropriate.	human_review
13-006	H	Graphics objects that possess semantic value only within a group of graphics objects is tagged on its own.	human_review
13-007	H	A more accessible representation is not used.	human_review
13-008	H	ActualText not present when a <Figure> is intended to be consumed primarily as text.	human_review

Checkpoint 14: Headings

Rule	How	Failure condition	Module
14-001	H	Headings are not tagged.	human_review
14-002	M	Does use numbered headings, but the first heading tag is not <H1>.	headings
14-003	M	Numbered heading levels in descending sequence are skipped (Example: <H3> follows directly after <H1>).	baseline, headings
14-004	H	Numbered heading tags do not use Arabic numerals and are not role mapped to heading types that do.	human_review
14-005	H	Content representing a 7th level (or higher) heading does not use an <H7> (or higher) tag.	human_review
14-006	M	A node contains more than one <H> tag.	headings
14-007	M	Document uses both <H> and <H#> tags.	headings

Checkpoint 15: Tables

Rule	How	Failure condition	Module
15-001	H	A row has a header cell, but that header cell is not tagged as a header.	human_review
15-002	H	A column has a header cell, but that header cell is not tagged as a header.	human_review
15-003	M	In a table not organized with Headers attributes and IDs, a <TH> cell does not contain a Scope attribute.	baseline, tables
15-004	H	Content is tagged as a table for information that is not organized in rows and columns.	human_review
15-005	H	A given cell's header cannot be unambiguously determined.	human_review

Checkpoint 16: Lists

Rule	How	Failure condition	Module
16-001	H	List is an ordered list, but no value for the ListNumbering attribute is present.	human_review
16-002	H	List is an ordered list, but the ListNumbering value is not Decimal, UpperRoman, LowerRoman, UpperAlpha or LowerAlpha.	human_review
16-003	H	Content is a list but is not tagged as a list.	human_review

Checkpoint 17: Mathematical Expressions

Rule	How	Failure condition	Module
17-001	H	Content is a mathematical expression but is not tagged with a <Formula> tag.	human_review
17-002	M	<Formula> tag is missing an Alt attribute.	math
17-003	M	Unicode mapping requirements are not met.	font_program

Checkpoint 18: Page Headers and Footers

Rule	How	Failure condition	Module
18-001	H	Headers and footers are not marked as pagination artifacts.	human_review
18-002	H	Header or footer artifacts are not classified as Header or Footer subtypes.	human_review

Checkpoint 19: Notes and References

Rule	How	Failure condition	Module
19-001	H	Footnotes or endnotes are not tagged as <Note>.	human_review
19-002	H	References are not tagged as <Reference>.	human_review
19-003	M	ID entry of the <Note> tag is not present.	notes
19-004	M	ID entry of the <Note> tag is non-unique.	notes

Checkpoint 20: Optional Content

Rule	How	Failure condition	Module
20-001	M	Name entry is missing or empty in an Optional Content Configuration Dictionary in the Configs array of OCProperties.	optional_content
20-002	M	Name entry is missing or empty in the Optional Content Configuration Dictionary that is the D entry of OCProperties.	optional_content
20-003	M	An AS entry appears in an Optional Content Configuration Dictionary.	optional_content

Checkpoint 21: Embedded Files

Rule	How	Failure condition	Module
21-001	M	The file specification dictionary for an embedded file does not contain F and UF entries.	embedded_files

Checkpoint 22: Article Threads

Rule	How	Failure condition	Module
22-001	H	Article threads do not reflect logical reading order.	human_review

Checkpoint 23: Digital Signatures

Rule	How	Failure condition	Module
23-001	–	No test specific to digital signatures is required; other provisions apply (form fields).	human_review (not applicable)

Checkpoint 24: Non-Interactive Forms

Rule	How	Failure condition	Module
24-001	H	Non-interactive forms are not tagged with the PrintFields attribute.	human_review

Checkpoint 25: XFA

Rule	How	Failure condition	Module
25-001	M	File contains the dynamicRender element with value "required".	xfa

Checkpoint 26: Security

Rule	How	Failure condition	Module
26-001	M	The file is encrypted but does not contain a P entry in its encryption dictionary.	security
26-002	M	The file is encrypted and does contain a P entry but the 10th bit position of the P entry is false.	security

Checkpoint 27: Navigation

Rule	How	Failure condition	Module
27-001	–	No tests specific to navigation are required; use appropriate semantics.	human_review (not applicable)

Checkpoint 28: Annotations

Rule	How	Failure condition	Module
28-001	H	An annotation is not in correct reading order.	human_review
28-002	M	An annotation, other than of subtype Widget, Link and PrinterMark, is not a direct child of an <Annot> structure element.	annot_struct, baseline
28-003	H	An annotation is used for visual formatting but is not tagged according to its semantic function.	human_review
28-004	M	An annotation, other than of subtype Widget, has neither a Contents entry nor an Alt entry on the enclosing structure element.	annot_struct, baseline
28-005	M	A form field has neither a TU entry nor an Alt entry on the enclosing structure element.	annot_struct, baseline
28-006	M	An annotation with subtype undefined in ISO 32000 does not meet 7.18.1.	annot_struct
28-007	M	An annotation of subtype TrapNet exists.	annot_struct
28-008	M	A page containing an annotation does not contain a Tabs entry.	annotations
28-009	M	A page containing an annotation has a Tabs entry with a value other than S.	annotations
28-010	M	A widget annotation is not nested within a <Form> tag.	annot_struct, baseline
28-011	M	A link annotation is not nested within a <Link> tag.	annot_struct
28-012	M	A link annotation does not include an alternate description in its Contents entry.	annot_struct
28-013	H	An IsMap entry is present with a value of true but the functionality is not provided in some other way.	human_review
28-014	M	CT entry is missing from the media clip data dictionary.	annot_struct
28-015	M	Alt entry is missing from the media clip data dictionary.	annot_struct
28-016	M	File attachment annotations do not conform to 7.11.	annot_struct
28-017	M	A PrinterMark annotation is included in the logical structure.	annot_struct
28-018	M	The appearance stream of a PrinterMark annotation is not marked as Artifact.	annot_struct

Checkpoint 29: Actions

Rule	How	Failure condition	Module
29-001	H	A script requires specific timing for individual keystrokes.	human_review

Checkpoint 30: XObjects

Rule	How	Failure condition	Module
30-001	M	A reference XObject is present.	dict_entries
30-002	M	Form XObject contains MCIDs and is referenced more than once.	xobjects

Checkpoint 31: Fonts

Rule	How	Failure condition	Module
31-001	M	A Type 0 font with a non-Identity encoding has different Registry values in the CIDFont and CMap CIDSystemInfo dictionaries.	fonts
31-002	M	A Type 0 font with a non-Identity encoding has different Ordering values in the CIDFont and CMap CIDSystemInfo dictionaries.	fonts
31-003	M	A Type 0 font with a non-Identity encoding has a CIDFont Supplement that is less than the CMap Supplement.	fonts
31-004	M	A Type 2 CID font contains neither a stream nor the name Identity as the value of the CIDToGIDMap entry.	fonts
31-005	M	A Type 2 CID font does not contain a CIDToGIDMap entry.	fonts
31-006	M	A CMap is neither a predefined CMap listed in ISO 32000-1 Table 118 nor embedded.	fonts
31-007	M	The WMode entry in a CMap dictionary is not identical to the WMode value in the CMap stream.	fonts
31-008	M	A CMap references another CMap which is not listed in ISO 32000-1:2008, 9.7.5.2, Table 118.	fonts
31-009	M	For a font used by text intended to be rendered the font program is not embedded.	baseline, fonts
31-010	H	A font program is embedded that is not legally embeddable for unlimited, universal rendering.	human_review
31-011	M	For a font used by text the font program is embedded but does not contain glyphs for all glyphs referenced for rendering.	font_program
31-012	M	An embedded Type 1 font has a CharSet string, but a glyph present in the font program is not listed in it.	font_program
31-013	M	An embedded Type 1 font has a CharSet string, but a glyph listed in it is not present in the font program.	font_program
31-014	M	An embedded CID font has a CIDSet stream, but a glyph present in the font program is not listed in it.	font_program
31-015	M	An embedded CID font has a CIDSet stream, but a glyph listed in it is not present in the font program.	font_program
31-016	M	For one or more glyphs, the width in the font dictionary and in the embedded font program differ by more than 1/1000 unit.	font_program
31-017	M	A non-symbolic TrueType font is used for rendering, but the embedded font program has no non-symbolic cmap subtable.	font_program
31-018	M	A non-symbolic TrueType font is used for rendering, but a rendered glyph cannot be looked up via any non-symbolic cmap subtable.	font_program
31-019	M	The font dictionary for a non-symbolic TrueType font does not contain an Encoding entry.	fonts
31-020	M	The font dictionary for a non-symbolic TrueType font has an Encoding dictionary without a BaseEncoding entry.	fonts
31-021	M	The Encoding or BaseEncoding of a non-symbolic TrueType font is neither MacRomanEncoding nor WinAnsiEncoding.	fonts
31-022	M	The Differences array of a non-symbolic TrueType font contains glyph names not listed in the Adobe Glyph List.	fonts
31-023	M	A non-symbolic TrueType font has a Differences array but the embedded font program has no (3,1) Microsoft Unicode cmap.	font_program
31-024	M	The Encoding entry is present in the font dictionary for a symbolic TrueType font.	font_program
31-025	M	The embedded font program for a symbolic TrueType font contains no cmap.	font_program
31-026	M	The embedded font program for a symbolic TrueType font has more than one cmap subtable but none is a (3,0) Microsoft Symbol cmap.	font_program
31-027	M	A font dictionary has no ToUnicode entry and no other permitted mechanism (standard encoding, AGL glyph names, Adobe CJK collection, non-symbolic TrueType) provides Unicode mapping.	baseline, font_program
31-028	M	One or more Unicode values specified in the ToUnicode CMap are zero (0).	font_program
31-029	M	One or more Unicode values specified in the ToUnicode CMap are equal to either U+FEFF or U+FFFE.	font_program
31-030	M	One or more characters used in text showing operators reference the .notdef glyph.	font_program

Horn extension rules

These ids do not correspond to a published Matterhorn condition. They catch PDF/UA prerequisites (a file that is not a tagged PDF cannot be PDF/UA), strong indicators of broken structure, and a few heuristics inherited from pdf_oxide.

Rule	Description	Module
00-x01	File header is not %PDF-1.0 … %PDF-1.7 or %PDF-2.0	file_syntax
00-x02	Non-whitespace bytes follow the final %%EOF	file_syntax
01-x01	/MarkInfo missing or /Marked not true (document is not a tagged PDF)	baseline, structure
01-x02	/StructTreeRoot missing or empty	structure
01-x03	/ParentTree missing or incomplete (a page /StructParents has no entry)	dict_entries
13-x01	Decorative graphic not marked as artifact (pdf_oxide heuristic)	baseline
13-x02	Figure caption not associated with its figure (pdf_oxide heuristic)	baseline
13-x03	Figure text lacks ActualText (pdf_oxide heuristic)	baseline
15-x01	Table has no TH header cells at all	baseline, tables
15-x02	Complex table without /Headers, /Scope or THead for header association	baseline, tables
15-x03	RowSpan/ColSpan values invalid or exceeding the table dimensions	tables
15-x04	Table rows do not span the same number of columns after RowSpan/ColSpan (irregular table, veraPDF 7.2-42/43)	tables
20-x01	Optional content group without a /Name	optional_content
26-x01	Encryption /P bit 5 (copy/extract) not set	security
28-x01	Link annotation has neither /A (action) nor /Dest	annotations, baseline
28-x02	Link text is not descriptive (pdf_oxide heuristic)	baseline
28-x03	Form field has no /T field name (pdf_oxide)	baseline
28-x04	Required form field not indicated (pdf_oxide)	baseline
28-x05	Form has no submit button (pdf_oxide)	baseline
31-x01	/CIDSystemInfo missing or incomplete (Registry/Ordering/Supplement)	fonts
31-x02	/CIDSet is not a valid stream	fonts
31-x04	/Differences array maps a code to .notdef	fonts

PDF/UA-2 (ISO 14289-2) rules

PDF/UA-2 is checked against ISO 14289-2:2024 directly: the Matterhorn Protocol 2.0 for PDF/UA-2 has not been published yet, so there is no official failure-condition index to cite. These rules use interim ids of the form ua2:<clause>-<test> (the ISO 14289-2 clause and a test number), which mirror the veraPDF PDF/UA-2 validation profile that PAC 2024 also follows; they will be re-mapped once Matterhorn 2.0 is released. They run only for documents whose XMP declares pdfuaid:part 2 (see horn coverage for the same list from your installed binary).

Requirements that PDF/UA-2 shares with PDF/UA-1 are reported under their Matterhorn 1.1 index by the regular checks. For PDF/UA-2 documents a few of those checks follow PDF 2.0 semantics:

• role mapping is resolved through PDF 2.0 namespaces (/NS, /RoleMapNS); types in the PDF 2.0 and MathML namespaces are never role mapped, and the Artifact structure type is accepted (02-001);
• an annotation enclosed in an Artifact structure element is an artifact and is exempt from the parent-type and accessible-text rules (28-002, 28-004, 28-010, 28-011, 28-012);
• a link annotation may be enclosed in a Reference element (28-011) and needs no /Contents when its Link/Reference element carries content or /Alt (28-012);
• pages with annotations may use /Tabs /A or /W as well as /S (28-009).

Horn validates 138/138 files of the veraPDF PDF/UA-2 corpus as expected (54/54 pass files compliant, 84/84 fail files detected).

Rule	Clause	Failure condition	Module
ua2:5-3	5	The 'part' property of the PDF/UA identification schema does not use the 'pdfuaid' namespace prefix.	ua2/identification
ua2:5-4	5	The 'rev' property of the PDF/UA identification schema does not use the 'pdfuaid' namespace prefix.	ua2/identification
ua2:5-5	5	pdfuaid:rev is missing or its value is not the four-digit year 2024.	ua2/identification
ua2:8.2.4-2	8.2.4	A circular role mapping exists in a namespace RoleMapNS.	ua2/structure
ua2:8.2.4-3	8.2.4	A structure type is role mapped to another type within the same namespace.	ua2/structure
ua2:8.2.5.2-1	8.2.5.2	The structure tree root does not contain a single Document element as its only child.	ua2/structure
ua2:8.2.5.2-2	8.2.5.2	The Document element is not in the PDF 2.0 namespace (http://iso.org/pdf2/ssn).	ua2/structure
ua2:8.2.5.8-1	8.2.5.8	A TOCI element has no Ref entry identifying the content it refers to.	ua2/structure
ua2:8.2.5.12-1	8.2.5.12	The generic H structure type is used; PDF/UA-2 requires numbered headings (Hn).	ua2/structure
ua2:8.2.5.14-1	8.2.5.14	The Note structure type is used; PDF 2.0 deprecates Note in favour of FENote.	ua2/structure
ua2:8.2.5.14-4	8.2.5.14	A FENote element has a NoteType attribute other than Footnote, Endnote or None.	ua2/structure
ua2:8.2.5.25-1	8.2.5.25	A list whose items contain Lbl elements has no ListNumbering attribute, or ListNumbering is None.	ua2/structure
ua2:8.2.5.25-2	8.2.5.25	An LI element contains content that is not enclosed in a Lbl or LBody element.	ua2/structure
ua2:8.2.5.20-2	8.2.5.20	Link annotations enclosed in the same Link or Reference element target different locations.	ua2/annotations
ua2:8.2.5.29-1	8.2.5.29	A MathML structure element is not a child of a Formula element (or of another MathML element).	ua2/structure
ua2:8.4.3-2	8.4.3	An ActualText entry contains Unicode private-use-area code points.	ua2/structure
ua2:8.4.3-3	8.4.3	An Alt entry contains Unicode private-use-area code points.	ua2/structure
ua2:8.8-1	8.8	An intra-document destination (outline item, link, GoTo action) is not a structure destination.	ua2/destinations
ua2:8.8-2	8.8	A GoTo action has no structure destination (SD entry).	ua2/destinations
ua2:8.9.2.2-1	8.9.2.2	An annotation with the Invisible flag is included in the logical structure and is not an artifact.	ua2/annotations
ua2:8.9.2.2-2	8.9.2.2	An annotation with the NoView flag (and without ToggleNoView) is included in the logical structure and is not an artifact.	ua2/annotations
ua2:8.9.2.4.7-1	8.9.2.4.7	A rubber stamp annotation has neither a Name nor a Contents entry.	ua2/annotations
ua2:8.9.2.4.8-1	8.9.2.4.8	An Ink annotation has no Contents entry.	ua2/annotations
ua2:8.9.2.4.9-1	8.9.2.4.9	A Popup annotation is included in the logical structure.	ua2/annotations
ua2:8.9.2.4.10-1	8.9.2.4.10	The file specification of a file attachment annotation has no AFRelationship entry.	ua2/annotations
ua2:8.9.2.4.11-1	8.9.2.4.11	A Sound annotation is present (deprecated in PDF 2.0, not permitted in PDF/UA-2).	ua2/annotations
ua2:8.9.2.4.11-2	8.9.2.4.11	A Movie annotation is present (deprecated in PDF 2.0, not permitted in PDF/UA-2).	ua2/annotations
ua2:8.9.2.4.12-1	8.9.2.4.12	A Screen annotation has no Contents entry.	ua2/annotations
ua2:8.9.2.4.13-1	8.9.2.4.13	A zero-size Widget annotation is included in the logical structure and is not an artifact.	ua2/annotations
ua2:8.9.2.4.19-1	8.9.2.4.19	A 3D annotation has no Contents entry.	ua2/annotations
ua2:8.9.2.4.19-2	8.9.2.4.19	A RichMedia annotation has no Contents entry.	ua2/annotations
ua2:8.9.4.2-1	8.9.4.2	An annotation's Contents entry differs from the Alt entry of its enclosing structure element.	ua2/annotations
ua2:8.10.1-2	8.10.1	A Form structure element contains more than one widget annotation.	ua2/annotations
ua2:8.10.2.3-1	8.10.2.3	A form field widget has neither a Lbl element in its Form structure element nor a Contents entry.	ua2/annotations
ua2:8.10.2.3-2	8.10.2.3	A form field widget with additional actions (AA) has no Contents entry.	ua2/annotations
ua2:8.11.1-2	8.11.1	The Metadata stream in the catalog lacks /Type /Metadata and /Subtype /XML.	ua2/identification
ua2:8.14.1-1	8.14.1	A file specification in the EmbeddedFiles name tree has no Desc entry.	ua2/identification

Notes on specific conditions

• 31-003 (Supplement) — the protocol text says the CIDFont Supplement must not be less than the CMap Supplement; ISO 14289-1 7.21.3.1 and the veraPDF corpus require it to be less than or equal. Horn follows ISO 14289-1: a CIDFont Supplement greater than the CMap Supplement fails.
• 15-x04 (irregular tables) — Matterhorn 01-006 NOTE 3 only suggests a warning for irregular tables, but the veraPDF PDF/UA-1 corpus (7.2-42, 7.2-43) treats them as failures, and header/data association cannot be determined for them. Horn reports them as failures.
• 17-003 — the Unicode requirements for <Formula> content are the general 10-001 / 31-027 requirements; Horn reports 17-003 when a document with <Formula> elements has a font that fails them.
• 28-006 — annotations with a subtype not defined in ISO 32000 are validated like any other annotation (28-002, 28-004); a failure is additionally reported under 28-006.
• 31-009 / 31-011 / 31-016 / 31-018 apply to glyphs used for rendering: text shown only in rendering mode 3 (invisible, e.g. OCR layers) is exempt, as required by the protocol.
• PDF/UA-2 rules follow the veraPDF PDF/UA-2 profile where ISO 14289-2 leaves room for interpretation: a TOCI without /Ref (ua2:8.2.5.8-1) and the deprecated Note type (ua2:8.2.5.14-1) are reported as failures, and structure destinations are required for every outline item, link and GoTo action (ua2:8.8-1, ua2:8.8-2).
• Manual review items are only emitted when the document contains the feature the condition is about (e.g. 15-001/15-002 only for documents with tables, 03-003 only when JavaScript is present, 31-010 always for embedded fonts, with a warning when the OS/2 fsType declares restricted embedding).

Check modules

Run horn list-checks to see the registered modules of your installed version.

Module	Checkpoint(s)	Scope
file_syntax	—	PDF header and end-of-file marker (extension) (2 rules)
baseline	various	pdf_oxide built-in PDF/UA-1 validator, mapped to Matterhorn ids (33 rules)
structure	01, 02	Tagged PDF prerequisites, role map termination, cycles and remapping (5 rules)
dict_entries	01, 02, 30	ParentTree, Suspects, unmapped types, reference XObjects (4 rules)
content_stream	01	Marked content: untagged content, artifact nesting (3 rules)
version	06	PDF/UA identification schema in XMP (2 rules)
metadata	06, 07, 11	XMP identifier and title, DisplayDocTitle, catalog language (5 rules)
language	11	BCP 47 tags and language context (6 rules)
nesting	09	Table, list, TOC, Ruby and Warichu nesting rules (5 rules)
headings	14	Heading hierarchy (4 rules)
tables	09, 15	Table structure, Scope, spans and grid regularity (6 rules)
lists	09	List structure (1 rules)
images	13	Figure alternative text (1 rules)
math	17	Formula alternative text (1 rules)
notes	19	Note IDs (2 rules)
optional_content	20	Optional content configurations (4 rules)
embedded_files	21	Embedded file specifications (1 rules)
xfa	25	Dynamic XFA (1 rules)
security	26	Encryption permissions (3 rules)
annotations	28	Tab order, link destinations (3 rules)
annot_struct	28	Annotation ↔ structure tree association, media clips, PrinterMark (13 rules)
xobjects	30	Structured Form XObjects painted once (1 rules)
fonts	31	Font embedding, composite-font CMaps, CIDToGIDMap, simple-font encodings (16 rules)
font_program	10, 17, 31	Embedded font programs: glyph coverage, CharSet/CIDSet, widths, TrueType cmaps, ToUnicode (18 rules)
ua2/identification	06, 21	PDF/UA-2: identification schema (part/rev), Metadata stream, embedded-file descriptions (5 rules)
ua2/structure	02, 09, 10, 14, 16, 17, 19	PDF/UA-2: PDF 2.0 namespaces, Document root, headings, lists, notes, MathML, private-use text (13 rules)
ua2/annotations	28	PDF/UA-2: annotation artifacts, annotation types, Contents/Alt, form widgets (17 rules)
ua2/destinations	27, 29	PDF/UA-2: structure destinations for outlines, links and GoTo actions (2 rules)
human_review	all	Manual-review items for the 48 human-judgment conditions (48 rules)