Data-model symbols in Latex

Here's a proposal:

documentclass{article}
usepackage{amsmath}

newcommand{ljoinrel}[1]{mathrel{mspace{-#1mu}}}
newcommand{negljoinrel}[1]{mathrel{mspace{#1mu}}}

newcommand{One}{%
  relbarljoinrel{4}relbarljoinrel{4}relbar
  ljoinrel{14}mapstocharnegljoinrel{14}%
}
newcommand{Many}{%
  relbarljoinrel{4}relbarljoinrel{4}relbar
  ljoinrel{14}<%
}
newcommand{Oone}{%
  relbarljoinrel{7}relbarljoinrel{7}relbarljoinrel{6}relbar
  ljoinrel{14}mapstocharnegljoinrel{6}mapstocharnegljoinrel{6}%
}
newcommand{Onemany}{%
  relbarljoinrel{4}relbarljoinrel{4}relbar
  ljoinrel{14}mapstochar<%
}
newcommand{Zeroone}{%
  relbarljoinrel{11}relbarjoinrel
  mathrel{circ}joinrel
  relbarljoinrel{8}mapstocharnegljoinrel{8}%
}
newcommand{Zeromany}{%
  relbarljoinrel{11}relbarjoinrel
  mathrel{circ}joinrel
  relbarljoinrel{14}<%
}

begin{document}

sbox0{$One$}showthewd0
sbox0{$Many$}showthewd0
sbox0{$Oone$}showthewd0
sbox0{$Onemany$}showthewd0
sbox0{$Zeroone$}showthewd0
sbox0{$Zeromany$}showthewd0

$A One B$

$A Many B$

$A Oone B$

$A Onemany B$

$A Zeroone B$

$A Zeromany B$

end{document}