Kroket Graph Description Language

Overall Conventions

Graphs are defined using a custom markup language.
Each markup describes an entity of the graph that can be parametrized using attributes.
Markups start with a < character, which must be followed by the name of the entity.
Markups end with the /> character sequence.

<entity  />

Attributes of an entity must be described within its markup delimiters.
The format is the following: name="value" (name is the attribute's name and value its value).
The value of an attribute must be quoted.

Example

<info title="Example" date="02/06/2010" />
<node id="n0" shape="circle" text="entry" text_style="bold" fill_color="#a9c3c3" />
<node id="n1" text="exit" text_color="red" stroke_style="dots" />
<edge id="e0" src_port="n0" src_style="open_dot" dest_port="n1" stroke_width="2" />
<group id="g0" contents="[n0, n1]" shape="rectangle" />

Available entities

info entity

The info entity is intended to contain general information related to the graph.
There should be only one info entity in a graph file.

Attributes of the info entity:

Name	Description	Type	Example	Mandatory	Default
title	Title of the graph	string	graph00	yes	n/a
comments	Short description of the graph	string	bla bla bla	no	empty
date	Date of creation or last modification	string	27/11/2010	no	empty
revision	Revision number	string	1.0	no	empty

node entity

The node entity describes a node of the graph.
Nodes are identified with a unique ID which should be different of any other ID used in the file.
The number of nodes is unlimited.

Attributes of the node entity:

Name	Description	Type	Example	Mandatory	Default
id	ID of the node	string	node00	yes	n/a
shape	Shape of the node	node shape	rectangle	no	ellipse
tags	Tags of the node	list of strings	[mammal, cat]	no	[ ]

Node shapes { rectangle, circle, ellipse }

The tags attribute enables the assignment of keywords to a node. This can be used for filtering purposes.

edge entity

The edge entity describes an edge of the graph. An edge connects two nodes.
Edges are identified with a unique ID which should be different of any other ID used in the file.
The number of edges is unlimited.

Attributes of the edge entity:

Name	Description	Type	Example	Mandatory	Default
id	ID of the edge	string	edge00	yes	n/a
src_port	Name of the source node's port the edge connects to	port name	node01/input	yes	n/a
dest_port	Name of the destination node's port the edge connects to	port name	node00/output	yes	n/a
src_style	Style of the connection to the source node	connection style	closed_dot	no	line
dest_style	Style of the connection to the destination node	connection style	dot	no	arrow
src_text	Label of the source's port	string	data Y out	no	empty
dest_text	Label of the destination's port	string	data X in	no	empty

Edge connection styles { line, arrow, closed_dot, closed_dot_arrow, open_dot, open_dot_arrow }

group entity

The group entity describes a group.
A group contains nodes which in some way - according to the semantic of the graph - are related to each other. It may contain subgroups as well.
The number of group entities is limited by the number of nodes, as a node can not belong directly to two groups at the same time. Otherwise, it is virtually unlimited.

Attributes of the group entity:

Name	Description	Type	Example	Mandatory	Default
id	ID of the group	string	grp00	yes	n/a
contents	IDs of the edges and nodes of the group	List of IDs	[node00, grp01, node01]	yes	n/a
shape	Shape of the group	group shape	ellipse	no	rectangle
expanded	State of the group	boolean	false	no	true

Group shapes { rectangle, ellipse }

The contents attribute of a group must be enumerated in a comma separated list.

Extra Attributes

The node, edge, and group entities share extra facultative attributes (mainly used for visual customization).

Name	Description	Type	Example	Default
fill_color	Color used for filling	string	red or #ff0000	white
fill_style	Style of the filling	filling style	solid	solid
stroke_color	Color used for stroking	string	green or #00ff00	black
stroke_style	Style of the stroking	stroking style	dashes	solid
stroke_width	Width of the stroking	integer	3	1
text	Label content	string	bla bla bla	empty
text_color	Font color used for the label	string	blue or #0000ff	black
text_style	Font style used for the label	label style ID	bold	normal
text_size	Font size used for the label	integer	8	10

Fill styles { nofill, solid, dots, cross }
Stroke styles { nostroke, solid, dashes, dots }
Text styles { normal, italic, bold }

A color is either a keyword or a numerical RGB specification.

Color keywords are: {red, blue, green, cyan, yellow, orange, white, black, gray}

The format of an RGB value in hexadecimal notation is a # character immediately followed by six hexadecimal characters.
Each pair of hexadecimal values represents the Red, Green or Blue component as in the following string: #rrggbb