Language Model

The Siddhi Language consists of following constructs.

Event Definitions
Queries
Calls to external functions (not supported in 1.0)

Following provides an abstract BNF based definition for Siddhi language.

<query> ::= <define-stream> | <execution-query>

<define-stream> ::= define stream <stream-name> <attribute-name> <type> {<attribute-name> <type>}

<execution-query>::= <input> <output> [<projection>]

<input> ::= from <streams>

<output> ::= ((insert [<output-type>] into <stream-name>) | (return [<output-type>]))

<streams> ::= <stream>[#<window>]

| <stream>#<window> [unidirectional] <join> [unidirectional] <stream>#<window> on <condition> within <time>

| [every] <stream> -> <stream> ... <stream> within <time>

| <stream>, <stream>, <stream> within <time>

<stream> ::= <stream-name> <condition-list>

<projection> ::= (<external-call> <attributelist>) | <attributelist> [group by <attribute-name> ][having <condition>]

<external-call> ::= call <name> ( <param-list> )

<condition-list> ::= {‘[’<condition>’]’}

<attributelist>::=(<attribute-name> [as <reference-name>]) | ( <function>(<param-list>) as <reference-name>)

<output-type> ::= expired-events | current-events | all-events

<param-list> ::= {<expression>}

<condition> ::= ( <condition> (and|or) <condition> ) | (not <condition>) | ( <expression> (==|!=|>=|<=|>|<|contains|instanceof) <expression> )