2.1.7 Window

A window is a time range set for the purpose of summarizing and analyzing stream data. It is defined in a query.

In order to summarize and analyze any data, you must clearly define a target scope. With stream data as well, you must first decide on a fixed range, and then process data in that range.

The following figure shows the relationship between stream data and the window.

Figure 2-6 Relationship between stream data and the window

[Figure]

The stream data (tuples) in the range defined by the window shown in this figure are temporarily stored in memory for processing.

A window defines the range of the stream data elements being processed, which can be defined in terms such as time, number of tuples, and so on. For details about specifying windows, see 2.2.2 Using data manipulation CQL to specify operations on stream data.