Biblatex: use doi only if there is no URL

Question

Is there a way to insert a doi of an entry only in case it is missing a URL field? It happens a lot that the doi and URL are essentially the same, and inserting them both yields a redundancy. I am using biblatex with biber.

PS: If you think this goal doesn't make sense please share your thoughts!

Answer 1

You can redefine the bibmacro doi+eprint+url so that the doi field is printed only if the url field is not defined, that is, add the following lines in the preamble:

\renewbibmacro*{doi+eprint+url}{%
  \iftoggle{bbx:doi}
    {\iffieldundef{url}{\printfield{doi}}{}}
    {}%
  \newunit\newblock
  \iftoggle{bbx:eprint}
    {\usebibmacro{eprint}}
    {}%
  \newunit\newblock
  \iftoggle{bbx:url}
    {\usebibmacro{url+urldate}}
    {}}

MWE

\documentclass{article}
\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}
\usepackage[backend=biber]{biblatex}

\addbibresource{\jobname.bib}

\renewbibmacro*{doi+eprint+url}{%
  \iftoggle{bbx:doi}
    {\iffieldundef{url}{\printfield{doi}}{}}
    {}%
  \newunit\newblock
  \iftoggle{bbx:eprint}
    {\usebibmacro{eprint}}
    {}%
  \newunit\newblock
  \iftoggle{bbx:url}
    {\usebibmacro{url+urldate}}
    {}}

\usepackage{filecontents}

\begin{filecontents}{\jobname.bib}
@article{kastenholz1,
  hyphenation = {american},
  author = {Kastenholz, M. A. and H{\"u}nenberger, Philippe H.},
  indextitle = {Computation of ionic solvation free energies},
  title = {Computation of methodology\hyphen independent ionic solvation free
    energies from molecular simulations},
  subtitle = {I. The electrostatic potential in molecular liquids},
  journaltitle = jchph,
  volume = {124},
  eid = {124106},
  date = {2006},
  url = {http://dx.doi.org/10.1063/1.2172593},
  urldate = {2006-10-01},
  doi = {10.1063/1.2172593},
}
@article{kastenholz2,
  hyphenation = {american},
  author = {Kastenholz, M. A. and H{\"u}nenberger, Philippe H.},
  indextitle = {Computation of ionic solvation free energies},
  title = {Computation of methodology\hyphen independent ionic solvation free
    energies from molecular simulations},
  subtitle = {I. The electrostatic potential in molecular liquids},
  journaltitle = jchph,
  volume = {124},
  eid = {124106},
  date = {2006},
  doi = {10.1063/1.2172593},
}
\end{filecontents}


\begin{document}
  \nocite{*}
  \printbibliography
\end{document}

Output:

As you can see the two entries are identical except for the url field, and if this field is defined, the doi field is not printed.

Answer 2

You can do this via mapping of datasources. The \DeclareSourcemap command

\DeclareSourcemap{
  \maps[datatype=bibtex]{
    \map{
      \step[fieldsource=url,final]
      \step[fieldset=doi,null]
    }  
  }
}

processes any bibtex input data and for each item in the bibliograhpy file it executes a number of commands given by \step:

• the first step fieldsource checks the url field

  • the instruction final means processing of the current entry is terminated if this field is empty or does not exist

• otherwise the next step fieldset=doi,null is executed; this clears the doi field, in fact it makes it look as if there was never a doi field in the input.

The result of this is that all biber/biblatex sees is an entry with either a url field or a doi field, but not both.

This has the advantage that you don't need to know how the particular biblatex style chooses to process these fields.

\documentclass{article}
\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}
\usepackage[backend=biber]{biblatex}

\addbibresource{\jobname.bib}

\DeclareSourcemap{
  \maps[datatype=bibtex]{
    \map{
      \step[fieldsource=url,final]
      \step[fieldset=doi,null]
    }  
  }
}

\usepackage{filecontents}

\begin{filecontents}{\jobname.bib}
@Article{Akbulut-S:deformations-G2,
  author =   {Akbulut, Selman and Salur, Sema},
  title =    {Deformations in {$G_2$} manifolds},
  journal =  {Adv. Math.},
  volume =   217,
  year =     2008,
  number =   5,
  pages =    {2130--2140},
  issn =     {0001-8708},
  doi =      {10.1016/j.aim.2007.09.009},
  url =      {http://dx.doi.org/10.1016/j.aim.2007.09.009}
}
@Article{Akbulut-S:deformations-G22,
  author =   {Akbulut, Selman and Salur, Sema},
  title =    {Deformations in {$G_2$} manifolds},
  journal =  {Adv. Math.},
  volume =   217,
  year =     2008,
  number =   5,
  pages =    {2130--2140},
  issn =     {0001-8708},
  url =      {http://dx.doi.org/10.1016/j.aim.2007.09.009}
}
@Article{Akbulut-S:deformations-G23,
  author =   {Akbulut, Selman and Salur, Sema},
  title =    {Deformations in {$G_2$} manifolds},
  journal =  {Adv. Math.},
  volume =   217,
  year =     2008,
  number =   5,
  pages =    {2130--2140},
  issn =     {0001-8708},
  doi =      {10.1016/j.aim.2007.09.009},
}

\end{filecontents}

\begin{document}
  \nocite{*}
  \printbibliography
\end{document}