GoJS tutorial part 2, listing 3

diagram.js

diagram.model = $(go.GraphLinksModel, {
	linkFromPortIdProperty: 'fromPort',
	linkToPortIdProperty: 'toPort',
	nodeDataArray: [
		// ...
	],
	linkDataArray: [
		{from: 1, to: 2, toPort: 'entry'},
		{from: 2, to: 3, fromPort: 'exit', toPort: 'entry'},
		{from: 1, to: 3, toPort: 'entry'},
		{from: 3, to: 4, fromPort: 'exit'}
	]
});