Depending on what they process, custom adaptors can be classified into the following two types:

• Data transmission application
  Receives input data and sends stream data to the SDP server.
  
• Data reception application
  Receives stream data for the result (query result) of an analysis by the SDP server.
  

The following figure shows where custom adaptors are positioned.

Figure 6-1 Positioning of custom adaptors

A data transmission application receives data in an arbitrary format and sends it as stream data to the stream data processing engine. A data reception application receives the stream data processed by the stream data processing engine and outputs it as data in an arbitrary format.