Metadata data and payload data in wso2 cep

what is metadata data and payload data in wso2 cep

I realized that these are three different types of data in the stream, but which have advantages over others that are not clear from any documentation. Or how we can use it in different situations.

All operations that can be performed on payload data, I could also do on meta and correlation data.

Can someone explain the difference with examples.


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There is no difference in how each of these attributes behave within the WSO2 CEP. It's just a logical separation, allowing the user to define streams with meta attributes, correlation attributes, and payload separately. You can use these attribute types if you need logical separation or just send data as payload if you don't need to separate metadata and correlation data.

You can store metadata related to a stream in metadata. for example attributes such as event_timestamp, request ip_address or similar. Similarly for correlation data, you can put attributes that are used to correlate events with other events from other streams. for example something like correlation_id. These attributes would be useful when performing merge operations on a stream.

Note, however, that the Siddhi engine used in CEP does not differentiate flows based on meta, correlation, payload, and does not process all attributes without any distinction. Attribute types are available for streams defined at the event-builder / event-formatter level that map to dense Siddhi streams at runtime to process requests.



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