Description of OpenAlea-Interface in GroIMP
-------------------------------------------

- GroIMP provides an HTTP-server on a arbitrary port (standard: 58070)
- data is transmitted via HTTP-POST
- variables for POST are:
	- "graph": the scene graph to operate on
	- "xlcode": the xl program
	- "command": the command(s) of the xl program to execute
- response of the HTTP-request depends on the status code:
	- status code 200 is transmitted when GroIMP run successfully
		-> the response string is the new scene graph
	- status code 400 is transmitted in an error case
		-> the response string is an error message

- the Webserver requires you to use the content-type application/x-www-form-urlencoded 
  to transfer the data to the server. But curl uses  multipart/form-data if you use the -F option. 
  You have to use --data or --data-urlencode instead. 

curl -X POST http://localhost:58070 --data "command=init;2run" --data-urlencode graph@sample.xeg --data-urlencode xlcode@sample.xl 

  With that command line curl produces the transformed graph as output.


graph
-----

- based on a new scene graph language called xeg (xml exchange graph)
- a xsd specification is avaiable
- basic configuration:
	<graph>
		type definitions for unknown node types (not in the standard)
		root node
		nodes
		edges
	</graph>
- type definition:
	<type name="XY">
		<extends name="Node">
		<!-- every node must inherit in its hierarchy from a standard node type -->
		<property name="z" type="float" />
		<!-- defines an attribute "z" with type "float" -->
	</type>
- root node:
	<root root_id="0" />
	<!-- the root node must have its own and unique id -->
- node:
	<node id="1" name="anyName" type="XY">
	<!-- id is unique, type is either a standard node type or a node type defined in this xeg string -->
   		<property name="z" value="12.34" />
   		<!-- same property as in definition with value -->
	</node>
- edge:
	<edge id="0" src_id="0" dest_id="1" type="successor" />
	<!-- an edge connects two nodes with a specific edge type -->
	<!-- edge types are "successor" and "branch" or any own label -->
- complete example:
	<graph>
	  <type name="XY">
	    <extends name="Node"/>
	    <property name="z" type="float" />
	  </type>
	  <root root_id="0" />
	  <node id="1" name="" type="XY">
	    <property name="z" value="12.34" />
	  </node>
	  <edge id="0" src_id="0" dest_id="1" type="successor" />
	</graph>

xlcode
------

- a standard xl program as used in GroIMP
- to use own defined node types, use an equivalent definition as in xeg string
- example:
	module XY extends Node {	
		float z;
	}
	
	protected void init() [
		Axiom ==> XY;
	]
	
	public void run() [
	    a:XY ==> a Cylinder;
	]

command
-------

- sequence of one ore more methods of the xl program
- methods must be public (except the "init"-method, which can be protected) and without parameters
- methods are separeted with semicolons
- to execute one method repeatedly, declare a number in front of the method name
- example: "init;3run" => execute one time the init-method, three times the run method