ClearSCADA expressions can be evaluated at a server or at a client depending on where they are being used. Expressions that are evaluated at a server can only include references to database items that are stored on that server—they cannot refer to items in other databases. Similarly, some functions are only available at the server.
When you are using expressions, you need to consider that:
- Expressions for Mimic animations and Trend titles and labels are evaluated by the client and so can reference items in other databases.
- Expressions for Group Templates, Data Grid cells, Data Set fields, Historic Calculations, and calling methods (user methods, alarm methods, and so on) are evaluated at a server and so can only include references to items that are on that specific server.
- Several functions are only available on servers or clients (see Functions).
WebX clients cannot support references that include a system (database).