How to add an academic title before the author name with \citeauthor?

Question

In French legal citation, one is supposed to refer to "professor X" or "Dean Y" when referring to an author in a sentence. Using biblatex and Biber, this would mean that \citeauthor{key} should prepend the right academic title (if any) before each author.

The idea would be to have a separate database (in whatever form) specifying an author name and the title to prepend, and to have biblatex look in the database whenever \citeauthor is called. Ideally, one could add names to the database by using a latex command such as \addauthor{X}{Professor}. I am not interested in having a macro for "professor" and another one for "dean".

Thus, I would like to know if such a system could be implemented (i.e. whether it would be reasonably simple and efficient, given that \citeauthor is not the most widely used command), and how to implement it.

Edit

Following Daniel E. Shub's idea of using the nameaddon field, I figured out a Biber solution that seems to work properly, although it requires having two \citeauthor commands for capitalisation purposes.

In the biber.conf file, I wrote the following (with actual last names instead of X, Y, Z):

<map>
    <map_step map_field_source="AUTHOR" map_match="X|Y" map_final="1"/>
    <map_step map_field_set="NAMEADDON" map_field_value="le professeur"/>
</map>
<map>
    <map_step map_field_source="AUTHOR" map_match="Z" map_final="1"/>
    <map_step map_field_set="NAMEADDON" map_field_value="le doyen"/>
</map>

And I modified the \citeauthor macro as described by Daniel, with a \CiteAuthor variant that applies the \MakeCapital formatting (for start of sentence citations).

Not sure this is the most aesthetic way of doing it, though… and, as mentioned, it only works for single author references.

Answer 1

Multiple-author works can be handled by adding academic distinctions as name prefixes via the biber sourcemap option. This biber.conf file maps data in the author field to namea. Distinctions are added to namea in a series of map steps.

<?xml version="1.0" encoding="UTF-8"?>
<config>
  <sourcemap>
    <maps datatype="bibtex">
    <map map_overwrite="1">
      <map_step map_field_source="AUTHOR" map_final="1"/>
      <map_step map_field_set="NAMEA" map_origfieldval="1"/>
      <map_step map_field_source="NAMEA"
                map_match="Knuth"
                map_replace="le professeur honoraire Knuth"/>
      <map_step map_field_source="NAMEA"
                map_match="Sigfridsson"
                map_replace="le docteur Sigfridsson"/>
      <map_step map_field_source="NAMEA"
                map_match="(Ryde|von Brandt|Bertram|Wentworth)"
                map_replace="le professeur $1"/>
      <map_step map_field_source="NAMEA"
                map_match="Erich Hoffmann"
                map_replace="le professeur Hoffmann, Erich"/>
    </map>
    </maps>
  </sourcemap>
</config>

Note that any author names following the <firstname lastname> format in the bib file need to be normalized to <prefix lastname, firstname> so that the prefix is parsed correctly. The last map step above gives an example.

A variant of \citeauthor that prints the distinctions can be defined a few different ways. In the document below this command is just \citeauthor, but we locally append the \AtEveryCitekey hook with code that resets labelname to namea and toggles useprefix to true.

\documentclass{article}
\usepackage[T1]{fontenc}
\usepackage[french]{babel}
\usepackage{csquotes}
\usepackage[backend=biber,maxcitenames=2]{biblatex}

\makeatletter
\newrobustcmd*{\citedistinctauthor}{%
  \AtNextCite{%
    \appto\blx@hook@citekey{%
      \savename{namea}{\cbx@namea}%
      \restorename{labelname}{\cbx@namea}%
      \toggletrue{blx@useprefix}}}%
  \citeauthor}
\makeatother

\newrobustcmd*{\Citedistinctauthor}{\bibsentence\citedistinctauthor}

\addbibresource{biblatex-examples.bib}

\begin{document}
\subsection*{\ttfamily\textbackslash citedistinctauthor}
\Citedistinctauthor{sigfridsson,bertram} show that...
Moreover \citedistinctauthor{knuth:ct,brandt,aristotle:poetics} show that...
\subsection*{\ttfamily\textbackslash citeauthor}
\Citeauthor{sigfridsson,bertram} show that...
Moreover \citeauthor{knuth:ct,brandt,aristotle:poetics} show that...
\printbibliography
\end{document}

Answer 2

If you are only dealing with single author works then a logical place for this extra information might be the nameaddon field. While the description for this field is information to be printed after the author name, it is not used in any standard bibliography styles. You would then need to modify \citeauthor to use this information.

Something like this:

\documentclass{article}
\usepackage[backend = biber]{biblatex}
\begin{filecontents}{\jobname.bib}
@Book{knuth,
  author = "Donald E. Knuth",
  title = "The {\TeX}book",
  publisher = "Addison-Wesley",
  year = "1986",
  nameaddon = "Professor",
}
\end{filecontents}
\addbibresource{\jobname.bib}


\DeclareCiteCommand{\citeauthor}
  {\boolfalse{citetracker}%
   \boolfalse{pagetracker}%
   \usebibmacro{prenote}}
  {\ifciteindex
     {\indexnames{labelname}}
     {}%
   \printfield{nameaddon}\addspace{}\printnames{labelname}}
  {\multicitedelim}
  {\usebibmacro{postnote}}


\begin{document}
The \TeX book is written by \citeauthor{knuth}.

\printbibliography
\end{document}