Developing Apama Applications > Developing Apama Applications in Event Modeler > Overview of Using Event Modeler > About scenario variables > Variable properties
Variable properties
Variable properties only apply to, and are enforced by, dashboards. That is, they only apply when a variable is presented to, and is interacted with by, an end user of the scenario. By design, variable properties do not apply to scenario rules or variable wiring within the Variables tab.
Each variable has a mutability property, which can take the following values:
*Mutable – This property is of relevance to the dashboard. If set it means that the end-user should be able to set and change the value of this variable at any time, via a dashboard.
*Immutable – This property is of relevance to the dashboard. If set it means that the end-user should only be allowed to set the value of this variable upon creation of the scenario instance, and should not be able to modify it afterwards.
*Fixed – This means that this variable is a constant; it cannot be modified through a dashboard. If a variable is set as Fixed but no value is provided for it in the Variables tab, the Event Modeler will automatically set it to the default value for its type.
Furthermore, each variable can also be set to be Unique. This means that if multiple instances of a scenario are started concurrently, the value of this variable must be unique across all instances. The dashboard used to enter values for this variable will ascertain that this is the case before accepting the value from the user. Note that if a variable is set to be Unique, it must also be Immutable.
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