private static MetaStreamEvent generateCUDMetaStreamEvent(boolean isProcessingOnExternalTime) {
        MetaStreamEvent metaStreamEvent = new MetaStreamEvent();
        Map<Attribute, int[]> cudInputStreamAttributesList =
                generateCUDInputStreamAttributes(isProcessingOnExternalTime);
        StreamDefinition inputDefinition = new StreamDefinition();
        for (Attribute attribute : cudInputStreamAttributesList.keySet()) {
            metaStreamEvent.addData(attribute);
            inputDefinition.attribute(attribute.getName(), attribute.getType());
        }
        metaStreamEvent.addInputDefinition(inputDefinition);
        metaStreamEvent.setEventType(MetaStreamEvent.EventType.DEFAULT);
        return metaStreamEvent;
    }
This is the parser class of incremental aggregation definition.
modules/siddhi-core/src/main/java/io/siddhi/core/util/parser/AggregationParser.java