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Events are the lifeline of WSO2 CEP/DAS. They not only process data as events, but also interact with external systems using events. Event is a unit of data, and an event stream is a sequence of events of a particular type. The type of events can be defined as an event stream definition. The following sections explain how to work with events in WSO2 CEP.

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PropertyDescription
Event Stream NameName of the event stream.
Event Stream VersionVersion of the event stream. (Default value is 1.0.0.)
Event Stream DescriptionDescription of the events stream. (This is optional.)
Event Stream Nick-NameNick-names of an event streams separated by commas. (This is optional.)
Stream Attributes

Stream Attributes contains the data of the event. These are divided into three logical separations to give more usability and maintenance to the user. It is not mandatory to have attributes in all three sections, but there should be at least one section with at least one attribute defined. Also attribute names should be unique within each section.

  • Meta Data: Contains the meta information of the events. (Referred to as  meta_<attribute name>.)
  • Correlation Data: Contains the correlation information of the events.  (Referred to as  correlation_<attribute name>.).
  • Payload Data: Contains the actual data that the event intends to have.  (Referred to as <attribute name>.)

It is recommended to have logistic separation but the internal system does not differentiate or give privilege based on above separations. Also please note if you edit and add another attribute to existing stream definition, other artifacts which are associated with the stream will be inactive. So that it is recommended to create a new stream definition with a version including the additional attribute.

For example consider following attributes which exist in a single event.

event_timestamp, request_IP_address, correlation_Id, price, symbol with there corresponding data types.

We can logically separate the above attributes as following.

  • Meta Data :- event_timestamp, request_IP_address (These describes the events itself)
  • Correlation Data :- correlation_Id (These correlates events with other events from other streams . These and will be useful when you perform a join operations on a stream)
  • Payload Data :- price,symbol( These are actual information/details of the event)

Adding an event stream 
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