Skip to main content

GraphML

Converting a Bigraph to GraphML​

The GraphML file format allows representing arbitrary graphs in an XML-based structure. More about GraphML can be found on the official website http://graphml.graphdrawing.org/. An easy start into the file format provides the GraphML Primer.

The next listing shows how to convert a pure bigraph that is depicted below into GraphML.

imgs The node identifiers are omitted in the figure.

As String​

PureBigraph pureBigraph = ...;
PureBigraph2GraphMLPrettyPrinter graphMLPrettyPrinter = new PureBigraph2GraphMLPrettyPrinter();
String s = graphMLPrettyPrinter.toString(pureBigraph);
System.out.println(s);

The encoded bigraph in GraphML is shown below.

<?xml version="1.0" encoding="UTF-8"?>
<graphml xmlns="http://graphml.graphdrawing.org/xmlns" xmlns:schemaLocation="http://graphml.graphdrawing.org/xmlns http://graphml.graphdrawing.org/xmlns/1.0/graphml.xsd" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:y="http://www.yworks.com/xml/graphml">
  <graph xmlns="" id="bigraph" edgedefault="undirected">
    <node id="0">
      <data key="d0">root</data>
    </node>
    <node id="v0">
      <data key="d0">node</data>
      <data key="d1">Zone1</data>
    </node>
    <edge id="v0:0" source="v0" target="0" directed="true" />
    <node id="v1">
      <data key="d0">node</data>
      <data key="d1">Zone2</data>
    </node>
    <edge id="v1:0" source="v1" target="0" directed="true" />
    <node id="v2">
      <data key="d0">node</data>
      <data key="d1">Robot</data>
      <port name="0" />
    </node>
    <edge id="v2:v0" source="v2" target="v0" directed="true" />
    <node id="v4">
      <data key="d0">node</data>
      <data key="d1">Zone3</data>
    </node>
    <edge id="v4:v1" source="v4" target="v1" directed="true" />
    <node id="v5">
      <data key="d0">node</data>
      <data key="d1">Object</data>
      <port name="0" />
    </node>
    <edge id="v5:v1" source="v5" target="v1" directed="true" />
    <node id="v3">
      <data key="d0">node</data>
      <data key="d1">Gripper</data>
      <port name="0" />
    </node>
    <edge id="v3:v2" source="v3" target="v2" directed="true" />
    <node id="v6">
      <data key="d0">node</data>
      <data key="d1">Ownership</data>
      <port name="0" />
    </node>
    <edge id="v6:v5" source="v6" target="v5" directed="true" />
    <node id="isFree">
      <data key="d0">outer</data>
    </node>
    <node id="rId">
      <data key="d0">outer</data>
    </node>
    <node id="canGrip">
      <data key="d0">outer</data>
    </node>
    <node id="belongsTo">
      <data key="d0">outer</data>
    </node>
    <hyperedge>
      <data key="d2">isFree</data>
      <endpoint node="v5" port="0" />
    </hyperedge>
    <hyperedge>
      <data key="d2">rId</data>
      <endpoint node="v2" port="0" />
    </hyperedge>
    <hyperedge>
      <data key="d2">canGrip</data>
      <endpoint node="v3" port="0" />
    </hyperedge>
    <hyperedge>
      <data key="d2">belongsTo</data>
      <endpoint node="v6" port="0" />
    </hyperedge>
  </graph>
  <key xmlns="" id="d0" for="node" attr.name="type" attr.type="string" />
  <key xmlns="" id="d1" for="node" attr.name="control" attr.type="string" />
  <key xmlns="" id="d2" for="node" attr.name="refName" attr.type="string" />
</graphml>

As OutputStream​

PureBigraph pureBigraph = ...;
PureBigraph2GraphMLPrettyPrinter graphMLPrettyPrinter = new PureBigraph2GraphMLPrettyPrinter();
graphMLPrettyPrinter.toOutputStream(pureBigraph, System.out);

Validation​

The GraphML Schema defines the syntax of GraphML. The XML schema of GraphML is provided with Bigraph Framework and supports syntax validation of the encoded bigraph.

An example is shown in the listing below.

import javax.xml.*;
import javax.xml.transform.*;
import javax.xml.transform.stream.*;
import javax.xml.validation.*;

// some code omitted

ByteArrayOutputStream os = new ByteArrayOutputStream();
graphMLPrettyPrinter.toOutputStream(pureBigraph, os);

// Schema is loaded from classpath resource within the Bigraph Framework jar dependency
URL resource = BigraphPrettyPrinter.class.getClassLoader().getResource("graphml.xsd");
SchemaFactory sf = SchemaFactory.newInstance(XMLConstants.W3C_XML_SCHEMA_NS_URI);
Schema schema = sf.newSchema(resource);
Validator validator = schema.newValidator();
Source xmlFile = new StreamSource(new ByteArrayInputStream(os.toByteArray()));
validator.validate(xmlFile);

If no exception is thrown, the XML file is said to be valid.