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first hg version after svn
author wolffd
date Tue, 10 Feb 2015 15:05:51 +0000
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+<!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML//EN">
+<!--
+    This is a generated document.  Do not edit.
+-->
+<HTML VERSION="2.0">
+<HEAD>
+<TITLE>The DOT Language</TITLE>
+</HEAD>
+<BODY BGCOLOR=white>
+<A NAME="top"></A>
+<H1 ALIGN=CENTER>The DOT Language</H1>
+<HR>
+The following is an abstract grammar defining the DOT language.
+Terminals are shown in bold font and nonterminals in italics.
+Literal characters are given in single quotes.
+Parentheses ( and ) indicate grouping when needed.
+Square brackets [ and ] enclose optional items.
+Vertical bars | separate alternatives.
+<TABLE>
+<TR>
+  <TD ALIGN=RIGHT><I>graph</I></TD>
+  <TD ALIGN=LEFT>:</TD>
+  <TD ALIGN=LEFT>[ <B>strict</B> ] (<B>graph</B> | <B>digraph</B>) [ <I>ID</I> ] <B>'{'</B> <I>stmt_list</I> <B>'}'</B></TD>
+</TR>
+<TR>
+  <TD ALIGN=RIGHT><I>stmt_list</I></TD>
+  <TD ALIGN=LEFT>:</TD>
+  <TD ALIGN=LEFT>[ <I>stmt</I> [ <B>';'</B> ] [ <I>stmt_list</I> ] ]</TD>
+</TR>
+<TR>
+  <TD ALIGN=RIGHT><I>stmt</I></TD>
+  <TD ALIGN=LEFT>:</TD>
+  <TD ALIGN=LEFT><I>node_stmt</I></TD>
+</TR>
+<TR>
+  <TD ALIGN=RIGHT></TD>
+  <TD ALIGN=LEFT>|</TD>
+  <TD ALIGN=LEFT><I>edge_stmt</I></TD>
+</TR>
+<TR>
+  <TD ALIGN=RIGHT></TD>
+  <TD ALIGN=LEFT>|</TD>
+  <TD ALIGN=LEFT><I>attr_stmt</I></TD>
+</TR>
+<TR>
+  <TD ALIGN=RIGHT></TD>
+  <TD ALIGN=LEFT>|</TD>
+  <TD ALIGN=LEFT><I>ID</I> <B>'='</B> <I>ID</I></TD>
+</TR>
+<TR>
+  <TD ALIGN=RIGHT></TD>
+  <TD ALIGN=LEFT>|</TD>
+  <TD ALIGN=LEFT><I>subgraph</I></TD>
+</TR>
+<TR>
+  <TD ALIGN=RIGHT><I>attr_stmt</I></TD>
+  <TD ALIGN=LEFT>:</TD>
+  <TD ALIGN=LEFT>(<B>graph</B> | <B>node</B> | <B>edge</B>) <I>attr_list</I></TD>
+</TR>
+<TR>
+  <TD ALIGN=RIGHT><I>attr_list</I></TD>
+  <TD ALIGN=LEFT>:</TD>
+  <TD ALIGN=LEFT><B>'['</B> [ <I>a_list</I> ] <B>']'</B> [ <I>attr_list</I> ]</TD>
+</TR>
+<TR>
+  <TD ALIGN=RIGHT><I>a_list</I></TD>
+  <TD ALIGN=LEFT>:</TD>
+  <TD ALIGN=LEFT><I>ID</I> [ <B>'='</B> <I>ID</I> ] [ <B>','</B> ] [ <I>a_list</I> ]</TD>
+</TR>
+<TR>
+  <TD ALIGN=RIGHT><I>edge_stmt</I></TD>
+  <TD ALIGN=LEFT>:</TD>
+  <TD ALIGN=LEFT>(<I>node_id</I> | <I>subgraph</I>) <I>edgeRHS</I> [ <I>attr_list</I> ]</TD>
+</TR>
+<TR>
+  <TD ALIGN=RIGHT><I>edgeRHS</I></TD>
+  <TD ALIGN=LEFT>:</TD>
+  <TD ALIGN=LEFT><I>edgeop</I> (<I>node_id</I> | <I>subgraph</I>) [ <I>edgeRHS</I> ]</TD>
+</TR>
+<TR>
+  <TD ALIGN=RIGHT><I>node_stmt</I></TD>
+  <TD ALIGN=LEFT>:</TD>
+  <TD ALIGN=LEFT><I>node_id</I> [ <I>attr_list</I> ]</TD>
+</TR>
+<TR>
+  <TD ALIGN=RIGHT><I>node_id</I></TD>
+  <TD ALIGN=LEFT>:</TD>
+  <TD ALIGN=LEFT><I>ID</I> [ <I>port</I> ]</TD>
+</TR>
+<TR>
+  <TD ALIGN=RIGHT><I>port</I></TD>
+  <TD ALIGN=LEFT>:</TD>
+  <TD ALIGN=LEFT><B>':'</B> <I>ID</I> [ <B>':'</B> <I>compass_pt</I> ]</TD>
+</TR>
+<TR>
+  <TD ALIGN=RIGHT></TD>
+  <TD ALIGN=LEFT>|</TD>
+  <TD ALIGN=LEFT><B>':'</B> <I>compass_pt</I></TD>
+</TR>
+<TR>
+  <TD ALIGN=RIGHT><I>subgraph</I></TD>
+  <TD ALIGN=LEFT>:</TD>
+  <TD ALIGN=LEFT>[ <B>subgraph</B> [ <I>ID</I> ] ] <B>'{'</B> <I>stmt_list</I> <B>'}'</B></TD>
+</TR>
+<TR>
+  <TD ALIGN=RIGHT><I>compass_pt</I></TD>
+  <TD ALIGN=LEFT>:</TD>
+  <TD ALIGN=LEFT>(<B>n</B> | <B>ne</B> | <B>e</B> | <B>se</B> | <B>s</B> | <B>sw</B> | <B>w</B> | <B>nw</B> | <B>c</B> | <B>_</B>)</TD>
+</TR>
+</TABLE>
+<P>
+The keywords <B>node</B>, <B>edge</B>, <B>graph</B>, <B>digraph</B>,
+<B>subgraph</B>, and <B>strict</B> are case-independent.
+Note also that the allowed compass point values are not keywords, so
+these strings can be used elsewhere as ordinary identifiers and, conversely,
+the parser will actually accept any identifier.
+<P>
+An <I>ID</I> is one of the following: 
+<MENU>
+<LI> Any string of alphabetic (<TT>[a-zA-Z\200-\377]</TT>) characters, underscores (<TT>'_'</TT>) or
+digits (<TT>[0-9]</TT>), not beginning with a digit;
+<LI> a number [<tt>-</tt>]<sup>?</sup>(<tt>.</tt>[<tt>0</tt>-<tt>9</tt>]<sup>+</sup>  | [<tt>0</tt>-<tt>9</tt>]<sup>+</sup>(<tt>.</tt>[<tt>0</tt>-<tt>9</tt>]<sup>*</sup>)<sup>?</sup> ); 
+<LI> any double-quoted string (&quot;...&quot;) possibly containing escaped 
+quotes (\&quot;)<SUP>1</SUP>;
+<LI> an <A NAME=html>HTML string</A> (&lt;...&gt;).
+</MENU>
+Note that in HTML strings, angle
+brackets must occur in matched pairs, and unescaped newlines are allowed.
+In addition, the content must be legal XML, so that the special XML
+escape sequences for &quot;, &amp;, &lt;, and &gt; may be necessary
+in order to embed these characters in attribute values or raw text.
+<P>
+Both quoted strings and HTML strings are scanned as a unit, so
+any embedded comments will be treated as part of the strings.
+<P>
+An <I>edgeop</I> is <TT>-></TT> in directed graphs and <TT>--</TT> in
+undirected graphs.
+<P>
+An <I>a_list</I> clause of the form <I>ID</I> is equivalent to
+<I>ID</I><TT>=true</TT>.
+<P>
+The language supports C++-style comments: <TT>/* */</TT> and <TT>//</TT>.
+In addition, a line beginning with a '#' character is considered a line
+output from a C preprocessor (e.g., #  34 to indicate line 34 ) and discarded.
+<P>
+Semicolons aid readability but are not required except in the rare case
+that a named subgraph with no body immediately preceeds an anonymous
+subgraph, since the precedence rules cause this sequence to be parsed as
+a subgraph with a heading and a body.
+Also, any amount of whitespace may be inserted between terminals.
+<P>
+As another aid for readability, dot allows single logical lines to
+span multiple physical lines using the standard C convention of a
+backslash immediately preceding a newline character. In addition, 
+double-quoted strings can be concatenated using a '+' operator.
+As HTML strings can contain newline characters, they do not support the
+concatenation operator.
+<H2>Semantic Notes</H2>
+If a default attribute is
+defined using a <B>node</B>,  <B>edge</B>, or  <B>graph</B> statement,
+or by an attribute assignment not attached to a node or edge, any object of the
+appropriate type defined afterwards will inherit this attribute value.
+This holds until the default attribute is set to a new value, from which
+point the new value is used. Objects defined before a default attribute
+is set will have an empty string value attached to the attribute once
+the default attribute definition is made.
+<P>
+Note, in particular, that a subgraph receives the attribute settings of
+its parent graph at the time of its definition. This can be useful; for
+example, one can assign a font to the root graph and all subgraphs will
+also use the font. For some attributes, however, this property is
+undesirable. If one attaches a label to the root graph, it is probably
+not the desired effect to have the label used by all subgraphs. Rather
+than listing the graph attribute at the top of the graph, and the
+resetting the attribute as needed in the subgraphs, one can simple defer
+the attribute definition if the graph until the appropriate subgraphs
+have been defined.
+<P>
+If an edge belongs to a cluster, its endpoints belong to that cluster.
+Thus, where you put an edge can effect a layout, as clusters are sometimes
+laid out recursively.
+<H2>Character encodings</H2>
+The DOT language assumes at least the ascii character set.
+Quoted strings, both ordinary and HTML-like, may contain non-ascii characters.
+In most cases, these strings are uninterpreted: they simply serve as
+unique identifiers or values passed through untouched. Labels, however,
+are meant to be displayed, which requires that the software be able to
+compute the size of the text and determine the appropriate glyphs. 
+For this, it needs to know what character encoding is used.
+<P>
+By default, DOT assumes the UTF-8 character encoding. It also accepts
+the Latin1 (ISO-8859-1) character set, assuming the input graph uses
+the <B><A HREF=attrs.html#a:charset>charset</A></B> attribute to 
+specify this. For graphs using other
+character sets, there are usually programs, such as <TT>iconv</TT>, which
+will translate from one character set to another.
+<P>
+Another way to avoid non-ascii characters in labels is to use HTML entities
+for special characters. During label evaluation, these entities are
+translated into the underlying character. This
+<a HREF="http://www.graphviz.org/doc/char.html">
+table</a> shows the supported entities, with their Unicode value, a typical
+glyph, and the HTML entity name. Thus, to include a lower-case Greek beta
+into a string, one can use the ascii sequence <TT>&amp;beta;</TT>. 
+In general, one should only use entities that are allowed in the output
+character set, and for which there is a glyph in the font.
+<HR>
+<OL TYPE="1">
+<LI> In quoted strings in DOT, the only escaped character is double-quote
+("). That is, in quoted strings, the dyad \" is converted to "; all other
+characters are left unchanged. In particular, \\ remains \\. Layout
+engines may apply additional escape sequences.
+</OL>
+</BODY>
+</HTML>