2.1.6 Query

A query defines the processing that is performed on stream data. Queries are written in a query definition file using CQL. For details about the query definition file, see the uCosminexus Stream Data Platform - Application Framework Setup and Operation Guide.

Queries define the following three types of operations:

The following figure shows the relationship between these operations.

Figure 2-5 Relationship between the operations defined by a query

[Figure]

A window operation retrieves stream data elements within a specific time window. The data gathered in this process (tuple group) is called an input relation.

A relation operation processes the data retrieved by the window operation. The tuple group generated in this process is called an output relation.

A stream operation takes the data that was processed by the relation operation, converts it to stream data and outputs it.

For details about each of these operations, see 2.2.2 Using data manipulation CQL to specify operations on stream data.

Stream data is processed according to the definitions in the query definition file used by the stream data processing engine. For details about the contents of a query definition file, see 2.2 Using CQL to process stream data. For query code examples, see 2.3 Implementation examples of using CQL to process stream data.