How to setup "smart citation commands"?

Question

The biblatex package comes with a bunch of example files. One of them is called 18-numeric-hybrid.tex. It contains the following text:

We define a dedicated citation command for online references which uses numerical labels instead of the author-year scheme. Instead of defining a dedicated command, it is also possible (and usually preferable) to build smart citation commands which are able to switch citation styles depending on the entry type (or other criteria).

Can anyone give me a hint how I can implement such a smart citation command the best way?

Answer 1

First of all I think Audrey is right in saying that one can only guess what the creator of the mentioned file has meant by "smart citation commands".

The link - Audrey posted - kind of helped me to come up with this MWE (please note, that my example is based on the idea of an hybrid style such as described in the 18-numeric-hybrid.tex example file of the biblatex package):

\documentclass{article}
\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}
\usepackage[american]{babel}
\usepackage{csquotes}
\usepackage[
    style=alphabetic,
    labelnumber,
    defernumbers,
    backend=biber,
]{biblatex}
\addbibresource{test.bib}

\begin{filecontents}{test.bib}
@BOOK{Author2001,
  author = {Alastname1, Afirstname1},
  title = {Title},
  year = {2001},
}
@BOOK{Author2002,
  author = {Blastname1, Bfirstname1 and Blastname2, Bfirstname2},
  title = {Title},
  year = {2002},
}
@ONLINE{Online2001,
  author = {Olastname1, Ofirstname},
  title = {Test Website},
  year = {2001},
  url = {http://www.test.de},
  urldate = {2013-08-28},
}
@ONLINE{Online2002,
  author = {Olastname2, Ofirstname},
  title = {Test Website},
  year = {2002},
  url = {http://www.test.de},
  urldate = {2013-08-28},
}
\end{filecontents}

% Renew \cite command for entries of the type online
\renewbibmacro*{cite}{%
    \ifentrytype{online}{%
        \printtext[bibhyperref]{%
            \printfield{prefixnumber}%
            \printfield{labelnumber}}}{%
        \printtext[bibhyperref]{%
            \printfield{prefixnumber}%
            \printfield{labelalpha}%
            \printfield{extraalpha}}}}

% Setup "online" environment for sub-bibliography
\defbibenvironment{online}
    {\list{
        \printtext[labelnumberwidth]{%
            \iffieldundef{shorthand}{%
                \printfield{prefixnumber}\printfield{labelnumber}}{%
                \printfield{shorthand}}}}{%
            \setlength{\labelwidth}{\labelnumberwidth}%
            \setlength{\leftmargin}{\labelwidth}%
            \setlength{\labelsep}{\biblabelsep}%
            \addtolength{\leftmargin}{\labelsep}%
            \setlength{\itemsep}{\bibitemsep}%
            \setlength{\parsep}{\bibparsep}}%
    \renewcommand*{\makelabel}[1]{\hss##1}}
    {\endlist}
    {\item}
\DeclareFieldFormat{labelnumberwidth}{\mkbibbrackets{#1}}


\begin{document}
Published source \cite{Author2002}. Online source \cite{Online2002}. Published source \cite{Author2001}. Online source \cite{Online2001}.

\printbibheading

\printbibliography[heading=subbibliography,title={Published Sources},nottype=online,omitnumbers]

\printbibliography[heading=subbibliography,title={Internet Sources},env=online,type=online,sorting=none]
\end{document}