diff --git a/README.md b/README.md
index 90c117f..4a77afa 100644
--- a/README.md
+++ b/README.md
@@ -110,6 +110,10 @@ The file [cpdfxmlm.ml](cpdfxmlm.ml) was written by Daniel Bünzli.
 
 The file [cpdfyojson.ml](cpdfyojson.ml) was written by Martin Jambon and others.
 
+The error descriptions for -verify-pdfua "matterhorn1.1" come from the PDF
+Association, and are licensed under the Creative Commons Attribution 4.0
+International license.
+
 Contact
 -------
 
diff --git a/cpdfua.ml b/cpdfua.ml
index 226ab9b..d66e6cd 100644
--- a/cpdfua.ml
+++ b/cpdfua.ml
@@ -1 +1,70 @@
 open Pdfutil
+
+exception MatterhornError
+
+let matterhorn_01_003 pdf = ()
+let matterhorn_01_004 pdf = ()
+let matterhorn_01_005 pdf = ()
+let matterhorn_01_007 pdf = ()
+let matterhorn_02_001 pdf = ()
+let matterhorn_02_003 pdf = ()
+let matterhorn_06_001 pdf = ()
+let matterhorn_06_002 pdf = ()
+let matterhorn_06_003 pdf = ()
+let matterhorn_07_001 pdf = ()
+let matterhorn_07_002 pdf = ()
+let matterhorn_09_004 pdf = ()
+let matterhorn_09_005 pdf = ()
+let matterhorn_09_006 pdf = ()
+let matterhorn_09_007 pdf = ()
+let matterhorn_09_008 pdf = ()
+let matterhorn_10_001 pdf = ()
+let matterhorn_11_001 pdf = ()
+let matterhorn_11_002 pdf = ()
+let matterhorn_11_003 pdf = ()
+let matterhorn_11_004 pdf = ()
+let matterhorn_11_005 pdf = ()
+let matterhorn_11_006 pdf = ()
+let matterhorn_13_004 pdf = ()
+
+let matterhorn =
+  [("01-003", "Content marked as Artifact is present inside tagged content.", "UA1:7.1-1", matterhorn_01_003);
+   ("01-004", "Tagged content is present inside content marked as Artifact.", "UA1:7.1-1", matterhorn_01_004);
+   ("01-005", "Content is neither marked as Artifact nor tagged as real content.", "UA1:7-1-2", matterhorn_01_005);
+   ("01-007", "Suspects entry has a value of true.", "UA1:7-1-11", matterhorn_01_007);
+   ("02-001", "One or more non-standard tag’s mapping does not terminate with a standard type.", "UA1:7.1-3", matterhorn_02_001);
+   ("02-002", "A circular mapping exists.", "UA1:7.1-4", matterhorn_02_003);
+   ("06-001", "Document does not contain an XMP metadata stream", "UA1:7.1-8", matterhorn_06_001);
+   ("06-002", "The XMP metadata stream in the Catalog dictionary does not include the PDF/UA identifier.", "UA1:5", matterhorn_06_002);
+   ("06-003", "XMP metadata stream does not contain dc:title", "UA1:7.1-8", matterhorn_06_003);
+   ("07-001", "ViewerPreferences dictionary of the Catalog dictionary does not contain a DisplayDocTitle entry", "UA1:7.1-9", matterhorn_07_001);
+   ("07-002", "ViewerPreferences dictionary of the Catalog dictionary contains a DisplayDocTitle entry with a value of false", "UA1:7.1-9", matterhorn_07_002);
+   ("09-004", "A table-related structure element is used in a way that does not conform to the syntax defined in ISO 32000-1, Table 337.", "UA1-7.2-1", matterhorn_09_004);
+   ("09-005", "A list-related structure element is used in a way that does not conform to Table 336 in ISO 32000-1.", "UA1-7.2-1", matterhorn_09_005);
+   ("09-006", "A TOC-related structure element is used in a way that does not conform to Table 333 in ISO 32000-1.", "UA1-7.2-1", matterhorn_09_006);
+   ("09-007", "A Ruby-related structure element is used in a way that does not conform to Table 338 in ISO 32000-1.", "UA1-7.2-1", matterhorn_09_007);
+   ("09-008", "A Warichu-related structure element is used in a way that does not conform to Table 338 in ISO 32000-1.", "UA1-7.2-1", matterhorn_09_008);
+   ("10-001", "Character code cannot be mapped to Unicode.", "UA1:7.2-2", matterhorn_10_001);
+   ("11-001", "Natural language for text in page content cannot be determined.", "UA1:7.2-3", matterhorn_11_001);
+   ("11-002", "Natural language for text in Alt, ActualText and E attributes cannot be determined.", "UA1:7.2-3", matterhorn_11_002);
+   ("11-003", "Natural language in the Outline entries cannot be determined.", "UA1:7.2-3", matterhorn_11_003);
+   ("11-004", "Natural language in the Contents entry for annotations cannot be determined.", "UA1:7.2-3", matterhorn_11_004);
+   ("11-005", "Natural language in the TU entry for form fields cannot be determined.", "UA1:7.2-3", matterhorn_11_005);
+   ("11-006", "Natural language for document metadata cannot be determined.", "UA1:7.2-3", matterhorn_11_006);
+   ("13-004", "<Figure> tag alternative or replacement text missing.", "UA1:7.3-3", matterhorn_13_004);
+  ]
+
+let test_matterhorn pdf =
+  option_map
+    (fun (name, error, section, test) ->
+      try test pdf; None with
+       | MatterhornError -> Some (name, error, section)
+       | e -> Some (name, "Incomplete", section)
+    )
+    matterhorn
+
+let test_matterhorn_print pdf =
+  iter (fun (name, error, section) -> Printf.eprintf "%s %s %s\n" name section error) (test_matterhorn pdf)
+
+let test_matterhorn_json pdf =
+  `List (map (fun (name, error, section) -> `Assoc [("name", `String name); ("section", `String section); ("error", `String error)]) (test_matterhorn pdf))
diff --git a/cpdfua.mli b/cpdfua.mli
index f27f96f..08bcbd0 100644
--- a/cpdfua.mli
+++ b/cpdfua.mli
@@ -1 +1,5 @@
 (** PDF/UA *)
+
+val test_matterhorn_print : Pdf.t -> unit
+
+val test_matterhorn_json : Pdf.t -> Cpdfyojson.Safe.t