DOT Language

Dot is an abstract grammar defining language. We can use dot to represent graphs also. In this post, I will show how different graphs can be generated with different codes from dot language. I will still use the Java api for dot language which I mentioned in GraphViz Java post.
Since these are just a few examples, you can find other attributes and styles from Graphviz dot attr page or the dot manual.

Simple Directed Graph

digraph G {
    A
    B
    A -> B
    A -> C;
}

Output

Notes
You see that you don't have to introduce each node at the beginning. Any node in the edges will automatically inserted.

Simple Graph without Edges

digraph G {
    A
    B
    C
    D
}

Output

Notes
From this example, we see that we have to introduce all edges if there are no edges that consists of these nodes.

Simple Undirected Graph

graph G {
    A
    B
    A -- B
    A -- C
}

Output

Different Shape and Colors for Nodes

graph G {
    A [shape=box, peripheries=2,color=black, style=filled, fontcolor=white]
    B [style=filled, color=gray84, fillcolor=gray84,fontcolor=white]
    C [color=red, style=filled, fontcolor=white]
    D [shape=polygon,sides=4,distortion=.7]
    A -- B
    A -- C
}

Output

Notes
You can find many different node styles in this manual.

Different Edge Styles

digraph G {
    A
    B
    C
    D
    A -> B [arrowhead=obox, style=dotted, color=red]
    A -> C [taillabel="tail"]
    A -> D [label="g'", weight=4]
}

Output

Notes
Heavier weight means shorter, straighter and more vertical the edge is.