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<a class="menucur" href="overview.html" title="How everything fits together">Overview</a>
<a class="menuind" href="#inout" title="Input/Output and data flow">Dataflow</a>
<a class="menuind" href="#layout" title="Storage vs. Layout">Layouts</a>
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<a class="menuext" href="layouter.html" title="How the layouter works">Layouter</a>
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<a class="menuext" href="syntax.html" title="Syntax rules for the text format">Syntax</a>
<a class="menuext" href="attributes.html" title="All possible attributes for graphs, nodes and edges">Attributes</a>
<a class="menuext" href="faq.html" title="Frequently Asked Questions and their answers">F.A.Q.</a>
<a class="menuext" href="tutorial.html" title="Tutorial for often used graph types and designs">Tutorial</a>
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<h1>Graph::Easy - Manual</h1>
<h2>Overview</h2>
<div class="text">
<a name="inout">
<h3>Input and Output</h3>
</a>
<p>
Here is an overview of the data flow. Input is shown green, while direct output of Graph::Easy
is shown orange. The nodes in white are part of Graph::Easy.
<br>
Nodes in yellow show some possible output formats enabled via third-party
applications like 'dot'.
</p>
<img src="img/dataflow.png" alt="Data flow of Graph::Easy" title="Data flow of Graph::Easy">
<p>
There are many ways to create the internal data necessary for
<code>Graph::Easy</code> to work with it:
</p>
<ul>
<li>Use the <a href="http://bloodgate.com/graph-easy/">interactive graph editor</a>
<li>Write a text in one of the formats Graph::Easy understands (Graphviz, Graph::Easy, VCG, GDL) and use
the command line utility <b><a href="http://search.cpan.org/~tels/Graph-Easy/bin/graph-easy"
title="graph-easy manual">graph-easy</a></b> to parse, convert and layout it.
(This script is installed as part of Graph::Easy.)
<li>Write Perl code (see below)
</ul>
<p> </p>
<p>
Here is a bit of example Perl code:
</p>
<pre>
use strict;
use Graph::Easy;
my $graph = Graph::Easy->new();
$graph->add_edge('Bonn', 'Berlin');
$graph->add_edge('Berlin', 'Bonn', 'train' );
</pre>
<p>
And here is the corrosponding textual description:
</p>
<pre>
[ Berlin ] -- train --> [ Bonn ]
[ Bonn ] --> [ Berlin ]
</pre>
<p>
As you can see, the textual description is a bit shorter. Wether you want to convert
your input data to text and then parse it, or convert it directly with Perl
code is up to you, of course.
</p>
<p>
Likewise, once you have your data in an <code>Graph::Easy</code> object, you can output it in the
format you desire.
</p>
<p>
Note that the textual description format allows you a round-trip: you can feed
it to the Parser, and then generate text again from the resulting <code>Graph::Easy</code> object.
</p>
<a name="layout">
<h3>Storage vs. Layout</h3>
</a>
<p>
Graph::Easy did use the <a href="http://search.cpan.org/~jhi/Graph/">Graph</a> module
to internally store and manage the graph data. Since v0.25, it no longer does so, instead
it stores the nodes/edges simply as Perl hashes and then accesses them directly.
If you want to know why, please ready this <a href="benchmark.html">page</a>.
<br>
Note that both the <code>Graph</code> and <code>Graph::Easy</code> modules do
<em>only</em> store a representation of the graph, but not a particular layout.
For instance the following graph (given in the Graph::Easy syntax, more on that below):
</p>
<pre>
[ A ] -> [ C ] -> [ D ]
[ C ] -> [ E ]
</pre>
<p>
can be laid out in (probably infinitely) many ways. Here are two examples:
</p>
<img src="img/example1.png" alt="Example layout of simple graph" class="float">
<pre class="graph">
+---+ +---+ +---+
| A | --> | C | --> | D |
+---+ +---+ +---+
|
|
v
+---+
| E |
+---+
</pre>
<div class="clear"></div>
<h3>Layouts</h3>
<p>
To generate a specific layout, you need a module that provides this functionality.
There are some possibilities for generating a layout from a graph via Perl:
</p>
<ul>
<li>Graph::Easy
<li><a href="http://www.graphviz.org/">dot</a> (via graphviz)
<li><a href="http://search.cpan.org/~pasky/Graph-Layderer/">Graph-Layderer</a>
<li><a href="http://search.cpan.org/~thospel/Graph-Layout-Aesthetic/">Graph-Layout-Aesthetic</a>
</ul>
<p>
There might be more - when I started with <code>Graph::Easy</code>, this were the options.
</p>
<p>
Unlike the others, <code>Graph::Easy</code> works on a checker-board tiled layout.
<br>
Note that the traditional way of placing the nodes <em>anywhere</em> does not enable you
to generate ASCII output, nor HTML. Well, it might be possible, but it is quite hard to
do when the edges don't run straight but all over the place :-)
</p>
<p>
That's one of the reasons for the existance of this project. :-P
</p>
</div><div class="text next">
<p>
Please continue with the chapter about the <a href="features.html">feature set</a>.
</p>
</div>
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Page created <span class="date">2005-08-07</span> by <a href="http://bloodgate.com/mail.html">Tels</a>.
Last update: <span class="date">2007-09-09</span>
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