In the list of process definitions, people should be able to navigate to the diagram.
In Explorer in the list of processes, a new action should be added in the last column called "Show diagram". Ideally the diagram should be shown as a popup.
ReadOnlyProcessDefinition processDefinition = ((RepositoryServiceImpl)repositoryService).getDeployedProcessDefinition(processDefinitionId);
String resourceName = processDefinition.getDiagramResourceName();
String deploymentId = processDefinition.getDeploymentId();
InputStream repositoryService.getResourceAsStream(String deploymentId, String resourceName);
In a later release (we'll put that in a separate jira issue) people should be able to navigate to the diagram that indicates the current position of that task in the process diagram.