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% Copyright 2006 by Till Tantau
%
% This file may be distributed and/or modified
%
% 1. under the LaTeX Project Public License and/or
% 2. under the GNU Free Documentation License.
%
% See the file doc/generic/pgf/licenses/LICENSE for more details.
\section{Entity-Relationship Diagram Drawing Library}
\begin{tikzlibrary}{er}
This packages provides styles for drawing entity-relationship
diagrams.
\end{tikzlibrary}
This library is intended to help you in creating E/R-diagrams. It defines
only very little new styles, but using these style |entity| instead of
saying |rectangle,draw| makes the code more expressive.
\subsection{Entities}
The package defines a simple style for drawing entities:
\begin{stylekey}{/tikz/entity}
This style is to be used with nodes that represent entity types. It
causes the node's shape to be set to a rectangle that is drawn and
whose minimum size and width are set to sensible values.
Note that this style is called |entity| despite the fact that it is
to be used for nodes representing entity \emph{types} (the
difference between an entity and an entity type is the same as the
difference between an object and a class in object-oriented
programming). If this bothers you, feel free to define a style
|entity type| instead.
\begin{codeexample}[]
\begin{tikzpicture}
\node[entity] (sheep) {Sheep};
\node[entity] (genome) [right=of sheep] {Genome};
\end{tikzpicture}
\end{codeexample}
\end{stylekey}
\begin{stylekey}{/tikz/every entity}
This stype is envoked by the style |entity|. To change the
appearance of entities, you can change this style.
\begin{codeexample}[]
\begin{tikzpicture}
[every entity/.style={draw=blue!50,fill=blue!20,thick}]
\node[entity] (sheep) {Sheep};
\node[entity] (genome) [right=of sheep] {Genome};
\end{tikzpicture}
\end{codeexample}
\end{stylekey}
\subsection{Relationships}
Relationships are drawn using styles that are very similar to the
styles for entities.
\begin{stylekey}{/tikz/relationship}
This style works like |entity|, only it is to be used for
relationships. Again, |relationship|s are actually relationship types.
\begin{codeexample}[]
\begin{tikzpicture}
\node[entity] (sheep) at (0,0) {Sheep};
\node[entity] (genome) at (2,0) {Genome};
\node[relationship] at (1,1.5) {has}
edge (sheep)
edge (genome);
\end{tikzpicture}
\end{codeexample}
\end{stylekey}
\begin{stylekey}{/tikz/every relationship}
Works like |every entity|.
\begin{codeexample}[]
\begin{tikzpicture}
[every entity/.style={fill=blue!20,draw=blue,thick},
every relationship/.style={fill=orange!20,draw=orange,thick,aspect=1.5}]
\node[entity] (sheep) at (0,0) {Sheep};
\node[entity] (genome) at (2,0) {Genome};
\node[relationship] at (1,1.5) {has}
edge (sheep)
edge (genome);
\end{tikzpicture}
\end{codeexample}
\end{stylekey}
\subsection{Attributes}
\begin{stylekey}{/tikz/attribute}
This style is used to indicate that a node is an attribute. To
connect an attribute to its entity, you can use, for example, the
|child| command or the |pin| option.
\begin{codeexample}[]
\begin{tikzpicture}
\node[entity] (sheep) {Sheep}
child {node[attribute] {name}}
child {node[attribute] {color}};
\end{tikzpicture}
\end{codeexample}
\begin{codeexample}[]
\begin{tikzpicture}[every pin edge/.style=draw]
\node[entity,pin={[attribute]60:name},pin={[attribute]120:color}] {Sheep};
\end{tikzpicture}
\end{codeexample}
\end{stylekey}
\begin{stylekey}{/tikz/key attribute}
This style is intended for key attributes. By default, the will
cause the attribute to be typeset in italics. Typcially, underlining
is used instead, but that looks ugly and it is difficult to
implement in \TeX.
\end{stylekey}
\begin{stylekey}{/tikz/every attribute}
This style is used with every (key) attribute.
\begin{codeexample}[]
\begin{tikzpicture}
[text depth=1pt,
every attribute/.style={fill=black!20,draw=black},
every entity/.style={fill=blue!20,draw=blue,thick},
every relationship/.style={fill=orange!20,draw=orange,thick,aspect=1.5}]
\node[entity] (sheep) at (0,0) {Sheep}
child {node [key attribute] {name}};
\node[entity] (genome) at (2,0) {Genome};
\node[relationship] at (1,1.5) {has}
edge (sheep)
edge (genome);
\end{tikzpicture}
\end{codeexample}
\end{stylekey}
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