Dear Pablo
Thanks for the quick response. I'm only just starting and many of the questions, as I say, will answer themselves when I get into the documentation properly. I'm sure pstricks will be workable (\usemodule[pstricks] doesn't generate an error, but when you actually try to use pstricks it fails - but there will be another way). Edmac is not likely to be needed for the books I have in mind, but it is essential for editions that I typeset from time to time with XeTeX and I don't think anything else will give me the same control (surprisingly, in ConText it seems to halt on encountering \newinsert - another TeX primitive that I often use for other purposes but which must have a differently named equivalent in Context).
\umirtenpointsevenfive
is just my own invented name forthe MinionPro typeface at 10.75pt with the features that you saw in my example (old-style numerals etc.) - but I'm sure Context's own system of calling specific font sizes will become clear to me shortly.
All that aside, it is definitely the tagging that I want to get working - my XeTeX-produced PDFs have no tagging, and automated tagging tools produce absolutely nothing - that won't be acceptable to repositories such as Perspectivia, which now quite rightly insists on PDFs that are compliant with the latest accessibility legislation.
I will try not to bombard the list with childish questions, though - there is much I need to learn quietly on my own before I can get a successfully formatted (and hopefully tagged) chapter, at which point I will no doubt need help with fine-tuning the output.
