Author name of \textcite as possessive

Question

When using biblatex I often use \textcite. Sometimes I want to write things like "Smith's (2000) formulation of x is" instead of "Smith (2000) formulates x as". How do I achieve this? Or more generally, how do I make the author's name output by \textcite to be in the possessive case? I'm mainly looking for a looking for an English variant. This mean that I want \textcite to be able to add "'s" to the author's name, e.g. to output

Knuth's (1984)

instead of

Knuth (1984)

Ideally I want a solution to be able to put any author's or authors' name in the possessive case and for it to be able to cope with other languages than English.

The following example might clarify what I'm asking for:

\documentclass{article}

\usepackage[style=authoryear-comp]{biblatex}

\usepackage{filecontents}

\begin{filecontents*}{database.bib}
@book{texbook,
    author  = {Donald E. Knuth},
    title   = {The {{\TeX}book}},
    publisher   = {Addison-Wesley},
    date    = {1984}
    }
\end{filecontents*}

\bibliography{database.bib}

\begin{document}

\textcite{texbook}% Standard use. Output: "Knuth (1984)"

\textcite{texbook}'s% Failed try to get output in the possesive case. Output: "Knuth (1984)'s"

Knuth's (1984)% The ouput that I want

\end{document}

Answer 1

This answer extends Philipp Lehman's method for generating a possessive labelname using a format alias. It should work for all variants of the standard author-year styles.

Note that the solution is bad for plural labelnames, where the possessive is formed with just ' and not 's. This case is probably very rare, though. Other languages may not be as easy to handle. For an example refer to a previous question, which considers Norwegian possessives.

\documentclass{article}
\usepackage[style=authoryear-comp]{biblatex}
\usepackage{filecontents}

\DeclareNameFormat{labelname:poss}{% Based on labelname from biblatex.def
  \ifcase\value{uniquename}%
    \usebibmacro{name:last}{#1}{#3}{#5}{#7}%
  \or
    \ifuseprefix
      {\usebibmacro{name:first-last}{#1}{#4}{#5}{#8}}
      {\usebibmacro{name:first-last}{#1}{#4}{#6}{#8}}%
  \or
    \usebibmacro{name:first-last}{#1}{#3}{#5}{#7}%
  \fi
  \usebibmacro{name:andothers}%
  \ifnumequal{\value{listcount}}{\value{liststop}}{'s}{}}

\DeclareFieldFormat{shorthand:poss}{%
  \ifnameundef{labelname}{#1's}{#1}}

\DeclareFieldFormat{citetitle:poss}{\mkbibemph{#1}'s}

\DeclareFieldFormat{label:poss}{#1's}

\newrobustcmd*{\posscitealias}{%
  \AtNextCite{%
    \DeclareNameAlias{labelname}{labelname:poss}%
    \DeclareFieldAlias{shorthand}{shorthand:poss}%
    \DeclareFieldAlias{citetitle}{citetitle:poss}%
    \DeclareFieldAlias{label}{label:poss}}}

\newrobustcmd*{\posscite}{%
  \posscitealias%
  \textcite}

\newrobustcmd*{\Posscite}{\bibsentence\posscite}

\newrobustcmd*{\posscites}{%
  \posscitealias%
  \textcites}

\begin{filecontents}{\jobname.bib}
@Article{bertram:sa,
  author = {Bertram, Aaron and Wentworth, Richard},
  shortauthor = {BW},
  title = {Gromov invariants for holomorphic maps on Riemann surfaces},
  journaltitle = {J.~Amer. Math. Soc.},
  volume = {9},
  number = {2},
  date = {1996},
  pages = {529--571}}
@Book{title,
  title = {A Book with No Author},
  date = {1933}}
@Book{shorthand,
  title = {A Book with No Author},
  shorthand = {ABWNA},
  date = {1933}}
@Book{label,
  label = {Fallback label},
  date = {1933}}
@Book{does,
  title = {A Book by the Does},
  author = {Doe, John and Doe, Jane},
  shortauthor = {{The Does}},
  date = {1990}}
\end{filecontents}

\addbibresource{\jobname.bib}
\bibliography{biblatex-examples}

\renewcommand{\baselinestretch}{1.25}

\begin{document}
\subsection*{cite with labelname}
posscite many authors: \posscite[3036]{aksin} \\
textcite shortauthor: \textcite[e.g.][3]{bertram:sa} \\
posscite shortauthor: \posscite[e.g.][4]{bertram:sa} \\
textcite shorthand: \textcite{kant:ku} \\
posscite shorthand: \posscite{kant:ku} \\
textcite compact: \textcite{aristotle:physics,aristotle:poetics} \\
posscite compact: \posscite{aristotle:physics,aristotle:poetics} \\
textcites: \textcites[3036]{aksin}[529]{bertram:sa} \\
posscites: \posscites[3036]{aksin}[529]{bertram:sa} \\
posscite with plural labelname (where this solution is bad): \posscite{does}
\subsection*{cite without labelname}
textcite shorthand: \textcite{shorthand} \\
posscite shorthand: \posscite{shorthand} \\
textcite title: \textcite{title} \\
posscite title: \posscite{title} \\
textcite label: \textcite{label} \\
posscite label: \posscite{label} \\
\end{document}

Answer 2

You could always define a "possessive cite" command yourself as follows:

\newcommand\posscite[1]{\citeauthor{#1}'s (\citeyear{#1})}

Although I can't promise it would look pretty or work properly for multiple author works...

Of course, properly speaking what you should do is use biblatex's own \DeclarCiteCommand and friends interface (and replace the parentheses with the right macro so that if you change the type of parens used, they change too...)