throws InvalidConfigurationException
{
String modid = getAttribute(elem, "module");
String port = getAttribute(elem, "port");
if (modid == null || port == null)
throw new InvalidConfigurationException("Incomplete plug definition.");
PipelineModule mod = mods.get(modid);
if (mod == null)
throw new InvalidConfigurationException("Reference to non-existing module: "+modid);
/*
if (is_target && !mod.getInputPipeNames().contains(port))
throw new InvalidConfigurationException(String.format("Module %s has no input port named %s.", modid, port));