Validity Expression
Validity Expression is the resource property that determines which Iotellect contexts are compatible with the resource. When a server is started or the validity expression itself is updated, Iotellect Server evaluates this expression for every context in the system. When processing a context, it becomes the Default Context for the expression resolution environment. If the expression evaluates to True, the server considers the resource valid for the current context, and:
For dashboards, installs an Open Dashboard action into this context
For reports, installs a Launch Report action into this context
For groups, adds this context into the group
For models, attaches a separate copy of the model to this context
 | The Validity Expression is often used to check the type of context. This is very useful for creating models or dashboards that work with certain types of devices or system resources. For example, to make a dashboard work with every SNMP device in the system, set the Validity Expression to This expression will resolve to |
| Dynamic groups use Validity Expression for consolidating devices of a certain type. For example, to make a group containing all printer devices in the system, set the Validity Expression to This expression will resolve to |
Validity Expression Resolution Environment: | |
Context which is being verified for validity. | |
None. | |
0 | |
Standard variables only. | |
Validity Expression Recalculation
The Validity Expression is calculated in the following cases:
On server startup, to initially associate the resource with all existing valid contexts
When a new context is created, to associate the resource with it if it's valid
When a Validity Expression itself is modified, it's recalculated for all context in the system, because a new set of contexts could become valid while others may no longer be valid.
When an event specified in Validity Update Rules is fired.
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