SQL Server 2008 R2: StreamInsight Event Models – EventShapes

Continuing on the theme of describing StreamInsight, the next major concept is the Event Model. Events in StreamInsight are made up of two sets of data. One set is the basic information required by the StreamInsight engine such as when an event occurred. The other set is the user data contained within the events, called the "payload".

You can define what is contained in the payload. It is effectively a .NET class or struct that exposes a set of public members. We'll talk more about the payload in another post.

I mentioned before that StreamInsight has details of when an event occurs. It's actually more flexible than just storing a date and time. The temporal information that is stored is determined by the Eventshape. Events have three potential shapes.

EventShape.Interval provides a start and stop time for an event and is used for events that have a duration. The times are stored as UTC.

EventShape.Point deals with events that occur at a single point in time. The start time is all that matters. An end time is available but it is defined as the start time plus one cronon (or the smallest granularity of time storage). We mostly tend to ignore the end time.

EventShape.Edge deals with events that occur over an interval but at the time an event is recorded, we only have the start time. Later the event is updated when we find out the end time.

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