Language Model

The Siddhi Language consists of following constructs.

1. Stream Definitions
2. Event Table Definitions
3. Partition Definitions
4. Queries
   
   1. Filters
   2. Windows
   3. Joins
   4. Patterns
   5. Sequences
5. Calls to external functions (not supported in 1.0)

Following provides an abstract BNF based definition for Siddhi language.

<execution-plan> ::= <define-parition> | <define-stream> | <define-table> | <execution-query>

<define-partition> ::= define partition <partition-id> by <partition-type> {, <partition-type>}

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

<define-table> ::= define table <table-id> ( <attribute-name> <type> {, <attribute-name> <type>} ) { from <table-type>.<datasource-name>:<database-name>.<table-name>}

<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> )

<expression> ::= ( <expression> (+ | - | / | * | %) <expression> ) | <attribute-name> | <int> | <long> | <double> | <float> | <string> | <time>

<time> ::= [<int>( years | year )]  [<int>( months | month )] [<int>( weeks | week )] [<int>( days | day )] [<int>( hours | hour )] [<int>( minutes | min | minute )] [<int>( seconds | second | sec )]

  [<int>( milliseconds | millisecond )]