Most notably, this subset supports ESQL expressions (see Use of ESQL in the service flow project tools) but not ESQL statements, procedures, or modules.
ESQL (Extended Structured Query Language) is a programming language provided by IBM WebSphere® Message Broker to define and manipulate data within a message flow (see Reference works describing ESQL).
The service flow project tools support a subset of the functionality of ESQL that is available in WebSphere Message Broker (see Supported features of ESQL).