Required variable "Could not be resolved"

Problem

You receive an error message stating "Required Variable "<Sheet.Parameter.Parameter Name>" at position 00 could not be resolved" when attempting to add a parameter to a Naming Rule.

Solution

When you add a new parameter to a Naming Rule using the drop down list, Xrev Transmit considers this parameter as "Required" by default. This error indicates that the sample sheet that is has retrieved from your Revit project has no value for this particular parameter. You can identify which sheet is causing the issue, by inserting the <Sheet.No> variable and looking at the preview in yellow.

There are a few ways to resolve this issue:

Ensure that this parameter has a value set on all sheets.
Specify the parameter as "Optional", for example:
```
<Sheet.Parameters.AEC Projects?>
```
Specify a "Default Value" to be used when the parameter cannot be resolved (Has no value or doesn't exist in the project). In the below example NA would be input for each blank value:
```
<Sheet.Parameters.AEC Projects=NA>
```

There is more information on Naming Rules and their advanced options here.