Extra Attributes

A rule is a database Streams object that enables the Streams client to perform an action when an event occurs and a particular condition is met. Rules Engine, which is built into Streams, evaluates the rules. When the rules are grouped, they are known as rule sets. Rule sets may be positive or negative. Stream tasks very much depend on the rules.

Stream Clients such as Capture, Apply, and Propagation processes utilize the rules to select or discard the events. For instance, capture rules dictate what events to be extracted and what events are discarded by a Capture process. The propagation rules specify dictate what events are to be sent out what events are discarded by a Propagation process. In the same way, apply rules determine what dictates, what events have applied, and what events have to be discarded by an Apply process.

Each rule has three distinct components:

• Rule Condition - The rule condition combines one or more expressions and conditions and returns a Boolean value which is a value of TRUE, FALSE or NULL. An expression is a combination of one or more values and operators.
   

• Rule Evaluation Context - This is an object that defines external data that can be referenced in the rule conditions. The external data can exist as variables, table data, or both.
   

• Rule Action Context - This is optional information associated with a rule that is interpreted by the Streams client of the rules engine when the rule is evaluated.