E-\TeX: Guidelines for future \TeX{} extensions, revisited

Frank Mittelbach

Shortly after Don Knuth announced \TeX~3.0 I gave a paper analyzing
\TeX{}'s abilities as a typesetting engine.
The abstract back then said:
\begin{quote}
  Now it is time, after ten years' experience, to step back and
  consider whether or not \TeX{}~3.0 is an adequate answer to the
  typesetting requirements of the nineties.

  Output produced by \TeX{} has higher standards than output generated
  automatically by most other typesetting systems.  Therefore, in this
  paper we will focus on the quality standards set by typographers for
  hand-typeset documents and ask to what extent they are achieved by
  \TeX.  Limitations of \TeX{}'s algorithms are analyzed; and missing
  features as well as new concepts are outlined.
\end{quote}

Now---two decades later---it is time to take another look and see what
has been achieved since then, and perhaps more importantly, what can
be achieved now with computer power having multiplied by a huge factor
and last not least by the arrival of a number of successors to \TeX{}
which have lifted some of the limitations identified back then.