if ( this.process == null ) { throw new MissingAttributeException( "process" ); }
checkObjectAttribute( "process", getProcess() );
    public void doTag(XMLOutput output) throws Exception    {        if ( this.process == null )        {            throw new MissingAttributeException( "process" );        }        ProcessContext context = getProcessContext();        ProcessEngine  engine  = getProcessEngine();        engine.call( getProcess(),                     context );    }