Package for parsing author data

I propose two solutions based on datatool. The first requires an external database1.csv file (in the mwe below it is produced by the filecontents environment). The second solution creates the database (named database2) directly in the .tex file through the commands:

DTLnewdb{database2}

newcommand{addauthor}[5]{
  DTLnewrow{database2}%
  DTLnewdbentry{database2}{num}{#1}
  DTLnewdbentry{database2}{email}{#2}
  DTLnewdbentry{database2}{address}{#3}
  DTLnewdbentry{database2}{other}{#4}
  DTLnewdbentry{database2}{name}{#5}
}

addauthor{1}{email1}{Alice's address}{other1}{Alice}
addauthor{2}{email2}{Bob's address}{other2}{Bob}
addauthor{3}{email3}{Markus's address}{other3}{Markus}

The command getauhor extracts from the line given as the first argument the value given in the second argument:

newcommand{getauthor}[2]{%
  DTLforeach*[DTLiseq{num}{#1}]
  {database1}%database label
  {num=num,email=email,address=address,other=other,name=name}% assignment
  {csname#2endcsname}
}

Here is a minimal working example:

documentclass{book}
usepackage{datatool}
%--------------------------------------------------
% First method
%--------------------------------------------------
begin{filecontents}[overwrite]{database1.csv}
    num,email,address,other,name
    1,email1,Address 1,Other 1, Isaak Bacharach
    2,email2,Address 2,Other 2, Reinhold Baer
    3,email3,Address 3,Other 3, Christian Bär
    4,email4,Address 4,Other 4, Wolf Barth
end{filecontents}

DTLloaddb{database1}{database.csv}
newcommand{getauthor}[2]{%
    DTLforeach*[DTLiseq{num}{#1}]
    {database1}%database label
    {num=num,email=email,address=address,other=other,name=name}% assignment
    {textbf{csname#2endcsname}}
}
%--------------------------------------------------
%Second method
%--------------------------------------------------
DTLnewdb{database2}
newcommand{addauthor}[5]{
DTLnewrow{database2}%
DTLnewdbentry{database2}{num}{#1}
DTLnewdbentry{database2}{email}{#2}
DTLnewdbentry{database2}{address}{#3}
DTLnewdbentry{database2}{other}{#4}
DTLnewdbentry{database2}{name}{#5}
}
addauthor{1}{email1}{Alice's address}{other1}{Alice}
addauthor{2}{email2}{Bob's address}{other2}{Bob}
addauthor{3}{email3}{Markus's address}{other3}{Markus}

newcommand{GetAuthor}[2]{%
    DTLforeach*[DTLiseq{num}{#1}]
    {database2}%database label
    {num=num,email=email,address=address,other=other,name=name}% assignment
    {textbf{csname#2endcsname}}
}

begin{document}

section{First method (texttt{database1.csv})}

The name of the forth entry is getauthor{4}{name}    
The address of the second entry is getauthor{2}{address}

section{Second method (texttt{database2})}

The name of the first entry is GetAuthor{1}{name}    
The address of the second entry is GetAuthor{2}{address}
    
end{document}

This can be done for example with expl3's property lists – I changed the syntax a little bit requiring some author ID instead of implying an incremented number (which could be realised as well, of course):

documentclass{article}

ExplSyntaxOn
tl_new:N l__innisfree_author_tl

cs_new_protected:Npn innisfree_add_author:nn #1#2
  {
    prop_if_exist:cF {l__innisfree_author_#1_prop}
      { prop_new:c {l__innisfree_author_#1_prop} }
    tl_set:Nn l__innisfree_author_tl {#1}
    keyval_parse:NNn
      __innisfree_value_missing:n
      __innisfree_set_property:nn
      {#2}
  }

cs_set_protected:Npn __innisfree_value_missing:n #1
  { prop_put:cnn {l__innisfree_author_ l__innisfree_author_tl _prop} {#1} {??} }

cs_set_protected:Npn __innisfree_set_property:nn #1#2
  { prop_put:cnn {l__innisfree_author_ l__innisfree_author_tl _prop} {#1} {#2} }
  
cs_new:Npn innisfree_get_author:nn #1#2
  { prop_item:cn {l__innisfree_author_#1_prop} {#2} }

NewDocumentCommand addauthor {mm}
  { innisfree_add_author:nn {#1} {#2} }

NewDocumentCommand getauthor {mm}
  { innisfree_get_author:nn {#1} {#2} }
ExplSyntaxOff

addauthor{a}{email = ..., address = ..., other = ..., name = Alice}
addauthor{b}{email = ..., address = Bob's address, other = ..., name = Bob}

begin{document}

getauthor{a}{name} par
getauthor{b}{address}

end{document}

---

Just for fun let's abuse acro as an alternative “solution”. Although this is not a completely serious suggestion it could be used quite safely, actually:

documentclass{article}

usepackage{acro}
DeclareAcroProperty{name}
DeclareAcroProperty{email}
DeclareAcroProperty{address}
DeclareAcroProperty{other}

newcommandaddauthor[2]{%
  DeclareAcronym{#1}{
    short = #1 , long = #1 , #2 ,
    tag = authors % a filter to separate them from ``real'' acronyms – not
                  % really necessary
  }%
}

newcommand*getauthor[2]{acrofield{#1}{#2}}

addauthor{a}{email = ..., address = ..., other = ..., name = Alice}
addauthor{b}{email = ..., address = Bob's address, other = ..., name = Bob}

begin{document}

getauthor{a}{name} par
getauthor{b}{address}

end{document}