Data items
- Last UpdatedNov 21, 2022
- 2 minute read
- PI System
- PI DataLink 2023 SP1
- Visualization
PI DataLink functions return data about specified PI System data items, either PI points or PI AF attributes. Functions might return recorded values from a database or computed values based on specified criteria or a specified expression.
When you define a function, you specify the paths to data items with the Data item, Expression, and Filter expression fields along with the optional Root path field. You can specify:
-
Fully qualified paths in the Data item, Expression, or Filter expression fields. A fully qualified path begins with two backslashes (\\) and evaluates to either a PI point or a PI AF attribute.
-
Partial paths in the Data item, Expression, or Filter expression fields and the common base path in the Root path field. PI point names or PI AF attribute names are examples of partial paths. PI DataLink combines the common base path with the partial path to set the full path that evaluates to either a PI point or PI AF attribute.
PI DataLink requires a full path to find the data item. To find a PI point, PI DataLink must know the Data Archive server to search and the point name. To find a PI AF attribute, PI DataLink must know the PI AF server, the database, the element, and any subelements or parent attributes. Use a pipe (|) to separate attributes from elements or parent attributes.
You can leave the Root path field blank if the Data item, Expression, and Filter expression fields contain a fully qualified path or a PI point on the default Data Archive server.
If specified, the Root path field indicates the common path to the specified data items.
|
Type of data item |
Content of root-path field |
|---|---|
|
PI point |
Data Archive server that stores the point or a blank to indicate the default Data Archive server. Valid entries include:
|
|
PI AF attribute |
PI AF server and database along with any elements, subelements, and parent attributes not specified in Data item. Valid entries include:
|