On 4/16/25 00:50, Matthias Weber wrote:
> Thanks Pablo, this is excellent news. There is no urgency, but I
> will be happy to try it out and use it.

Matthias,

there is another approach with some cheating that may also work.

The attached PDF document is the compilation from the source below.

First you have to add math tagging in lpdf-tag-imp-testing.lmt (right
after "-- no math here"):

       math               = { pua = "ua1", pdf = "Formula" },
       inlinemath         = { pua = "ua1", pdf = "Formula" },
       displaymath        = { pua = "ua1", pdf = "Formula" },

Then you need to patch lpdf-tag.lmt:

--- lpdf-tag.lmt        2025-04-15 19:44:55.157060209 +0200
+++ mkxl/lpdf-tag.lmt   2025-04-16 06:26:56.731391047 +0200
@@ -1062 +1062 @@
-             -- Alt        = alternate,
+                Alt        = actualtext or nil,
@@ -1064 +1064 @@
-                ActualText = actualtext or nil,
+             -- ActualText = actualtext or nil,
@@ -1090 +1090 @@
-             -- Alt        = alternate,
+                Alt        = actualtext or nil,
@@ -1092 +1092 @@
-                ActualText = actualtext or nil,
+             -- ActualText = actualtext or nil,
@@ -1141 +1141 @@
-            Alt  = pdfunicode(label ~= "" and label or "image"),
+         -- Alt  = pdfunicode(label ~= "" and label or "image"),
@@ -1142,0 +1143 @@
+        parent.dict.Alt  = pdfunicode(label ~= "" and label or "image")

And it should work for PDF/UA-1. Please, don’t forget that I don’t use
math in ConTeXt at all (only for these testings).

Source for the attached PDF document:

  \enabledirectives [backend.usetags=testing]
  \setupstructure[state=start]
  \setupbackend
    [format=PDF/A-3a,
     intent=sRGB IEC61966-2.1,
     level=0]
  \setupbackend[format=pdf/ua-1]

  \setuptagging[state=start]

  \registermathsymbol[default][en]["1D467][the variable]
  \registermathsymbol[default][en]["1D458][the index]

  \starttext
  \startformula
    \abs {(z__0 + h)^n -  z__0^n }
    \alignhere
    = \abs {\sum_{k = 1}^n \binom{n}{k} h^k z__0^{n - k} }
    \breakhere
    = \abs {h \sum_{k = 0}^{n - 1} \binom{n}{k + 1} h^k z__0^{n - 1 - k} }
    \breakhere
    = \abs {h \sum_{k = 0}^{n - 1} \frac {n}{k + 1} \binom{n - 1}{k} h^k
  z__0^{n - 1 - k} }
    \breakhere
    \le  n \abs{h} \sum_{k = 0}^{n - 1}  \binom{n - 1}{k} \abs{h}^k
  \abs{z__0}^{n - 1 - k}
    \breakhere
    \le  n \abs{h} (\abs{z__0} + \abs{h})^{n - 1}
  \stopformula

  \registermathsymbol[default][en][lowercasebold][the vector]

  \startformula
    (\alpha + \beta) \mathbf{u} = \alpha \mathbf{u} + \beta \mathbf{u}
  \stopformula

  \stoptext

I hope it helps,

Pablo

Attachment: tagged-math.pdf
Description: Adobe PDF document

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