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<TITLE>Node, Edge and Graph Attributes</TITLE>
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<H1 align=CENTER>Node, Edge and Graph Attributes</H1>
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The table below describes the attributes used by various Graphviz tools.
The table gives the name of the attribute, the graph components (node,
edge, etc.) which use the attribute and the type of the attribute
(strings representing legal values of that type). Where applicable, the table
also gives a default value for the attribute, a minimum allowed setting
for numeric attributes, and certain restrictions on the use of the attribute.
<P>
Note that attribute names are case-sensitive. 
This is usually true for attribute values as well, unless noted.
<P>
All Graphviz attributes are specified by name-value pairs. Thus, to
set the fillcolor of a node <TT>abc</TT>, one would use
<TABLE>
<TR><TD><TT>abc [fillcolor = red]</TT></TR>
</TABLE>
Similarly, to set the arrowhead style of an edge <TT>abc -> def</TT>,
one would use
<TABLE>
<TR><TD><TT>abc -> def [arrowhead = diamond]</TT></TR>
</TABLE>
Further details concerning the setting of attributes can be found
in the description of the
<A HREF=lang.html>DOT language.</A>
<P>
At present, most device-independent units are either inches or
<A NAME="points"></A>
<A HREF="http://en.wikipedia.org/wiki/Point_(typography)">points</A>,
which we take as 72 points per inch.
<P>
<A NAME=h:undir_note><STRONG>Note:</STRONG></A> Some attributes, such as
<A HREF=#d:dir>dir</A> or <A HREF=#d:arrowtail>arrowtail</A>, are
ambiguous when used in
<A HREF=lang.html>DOT</A>
with an undirected graph since the head and tail of an edge are meaningless.
As a convention, the first time an undirected edge appears, the
<A HREF=lang.html>DOT</A>
parser will assign the left node as the tail node and the right node as
the head. For example, the edge <TT>A -- B</TT> will have tail <TT>A</TT>
and head <TT>B</TT>. It is the user's responsibility to handle such
edges consistently. If the edge appears later, in the format
<TABLE>
<TR><TD><TT>B -- A [taillabel = "tail"]</TT></TR>
</TABLE>
the drawing will attach the tail label to node <TT>A</TT>.
To avoid possible confusion when such attributes are required, the user
is encouraged to use a directed graph.
If it is important to make the graph appear undirected, this can be
done using the <A HREF=#d:dir>dir</A>, <A HREF=#d:arrowtail>arrowtail</A>
or <A HREF=#d:arrowhead>arrowhead</A> attributes.
<P>
The tools accept standard C representations for <EM>int</EM> and
<EM>double</EM> types.
For the <A NAME=k:bool><EM>bool</EM></A> type, TRUE values are
represented by "true" or "yes" (case-insensitive)
and any non-zero integer, and FALSE values by "false" or "no" (case-insensitive)
and zero.
In addition, there are a variety of specialized types such as
<EM>arrowType</EM>, <EM>color</EM>,
<EM>point</EM> and <EM>rankdir</EM>. Legal values for these types are given
at the end.
<P>
In the <A NAME=h:uses><STRONG>Used By</STRONG></A> field, the
characters E, N, G, S and C
represent edges, nodes, the root graph, subgraphs
and cluster subgraphs, respectively.
This field indicates which graph component uses the attribute.
<P>
In the <STRONG>Notes</STRONG> field, an annotation of <em>write only</em> 
indicates that the attribute is used for output, and is not used or read by any
of the layout programs.
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