a way to use bibliography utf8 @string entry keys

Question

Any suggestions how to allow UTF-8 @string macros in the mwe.bib file? [lines 537-539]

@string{          Uà   =   {Università} #.                           }
@string{        Uàdi   =   Uà#di                                     }
@string{      UàdSdi   =   Uà#degli# {Studi} #di                     }

@PhdThesis{mwe,
  author =   {Some Guy},
  title =    {On something},
  school =   Uàdi# {Padova},
  %school =      UàdSdi# {Bologna},
  year =     2010,
}

I have this setup:

\RequirePackage[T1]{fontenc}
\RequirePackage[utf8]{inputenc}
\RequirePackage{newunicodechar}
\RequirePackage[backend=biber%
,bibencoding=utf8,texencoding=utf8,style=numeric-comp%
,sorting=none,sortcites=true,block=none,indexing=false%
,citereset=none,isbn=true,url=true,doi=true]{biblatex}%

and use this in mwe.tex:

\addglobalbib[datatype=bibtex,type=file]{mwe.bib}
\begin{document}
\cite{mwe}
\printbibliography
\end{document}

then run:

biber mwe

and get:

WARN - BibTeX subsystem: /tmp/I5WGNx_9Fe/mwe.bib_16327.utf8, line 537, warning: overriding existing definition of macro "u"
ERROR - BibTeX subsystem: /tmp/I5WGNx_9Fe/mwe.bib_16327.utf8, line 538, syntax error: found "di", expected "="

Answer 1

Your given MWE has several errors, so I tried to correct it. As @egreg mentioned in his comment don't use special characters in string names. If you use something like di in a string (see your MWE) it is interpreted as macro. So define a string di or just use {...} to make clear it should be inserted as normal text. Please see the changed string definitions in my MWE.

I do not know the used language so I just guessed to build the following without an error or warning (the warning that mwe.bib (\jobname.bib gives mwe.bib, if your texfile is stored as mwe.tex) is overwritten is correct and can be ignored) compiling:

%http://tex.stackexchange.com/questions/74037/a-way-to-use-bibliography-utf8-string-entry-keys
\RequirePackage{filecontents}
\begin{filecontents*}{\jobname.bib}
@string{          Ua = {Universit\`a } #.             }
@string{        Uadi = Ua#{ di }                      }
@string{      UadSdi = Ua#{ degli }# { Studi } #{ di }}

@PhdThesis{mwe,
  author = {Some Guy},
  title  = {On something},
  school = Uadi# {Padova},
  year   = 2010,
}
@PhdThesis{mwe1,
  author = {Some Guy},
  title  = {On something},
  school = UadSdi# {Bologna},
  year   = 2010,
}
\end{filecontents*}

\documentclass{article}
\usepackage[T1]{fontenc}
\usepackage[utf8]{inputenc}
\usepackage{newunicodechar}
\usepackage[%
  backend=biber
 ,bibencoding=utf8
 ,texencoding=utf8
 ,style=numeric-comp
 ,sorting=none
 ,sortcites=true
 ,block=none
 ,indexing=false
 ,citereset=none
 ,isbn=true
 ,url=true
 ,doi=true
]{biblatex}%

\addglobalbib[%
   datatype=bibtex
  ,type=file
  ,backend=biber
]{\jobname.bib}
\begin{document}
\cite{mwe} \cite{mwe1}
\printbibliography
\end{document} 

If I missunderstood you please feel free to change my given MWE.