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TMDL view lets you script, modify, and apply changes to semantic model objects with a modern code editor using Tabular Model Definition Language (TMDL) in Power BI Desktop, improving development efficiency and providing complete visibility and control over semantic model metadata.
TMDL view offers an alternative experience to semantic modeling using code, instead of a graphical user interface such as Model view.
TMDL view offers the following advantages:
To use TMDL view, you must enable the preview feature. In Power BI Desktop select File > Options and settings > Options > Preview features and select the box next to TMDL View.
In Power BI Desktop, select the TMDL view icon located along the left side of the window, as shown in the following image.
When TMDL view opens the code editor is initially empty. You can script any semantic model object such as a table, measure, or column by selecting the objects from the Data pane and dragging them onto the code editor:
When using TMDL view and dragging the object from the Data pane, Power BI scripts the entire object metadata into the current tab as TMDL, or opens a new tab if the current tab isn't empty, as a createOrReplace TMDL script of the selected objects, as shown in the following image:
Alternatively, you can right-click an object in the Data view and select Script TMDL to new tab or to the clipboard, shown in the following image:
Tip
Multi selection is supported by pressing the CTRL key before scripting the objects into the TMDL view code editor.
Once you've scripted a semantic model object or pasted TMDL script into the code editor, you can use the comprehensive code experience features offered by the TMDL view code editor. The code experience features enable you to either explore the model metadata, or make modifications that can later be applied to the semantic model.
Semantic highlighting is built into the code editor, which improves readability by applying different colors to parts of your code based on meaning. Such color coding makes it easier to understand the structure and functionality of your TMDL code, as shown in the following image.
You can also expand or collapse sections of your TMDL script, as shown in the following image:
Autocomplete is built into the code editor, and offers intelligent suggestions while you type. Autocomplete can speed up your workflow, reduce the chance of errors, and help you understand your code options by dynamically suggesting possible values or properties by taking into consideration the cursor position.
You can also trigger the autocomplete feature in any location by pressing Ctrl+Space.
The code editor's built-in error diagnostics help you identify and fix issues by highlighting TMDL language errors in the code editor, with detailed messages that provide guidance on resolving them. Additionally, an error summary is available in the Problems pane, allowing easy navigation to the error location in the code editor, as shown in the following image.
When you're ready, you can select the Apply button to execute the TMDL script against the semantic model, and have your TMDL code changes applied.
When successful, a notification is displayed and your modeling change are applied to the semantic model.
In the event of a failure, an error notification is displayed to show that your modeling changes weren't applied to the semantic model. You can view more information about the error by selecting the Show details link in the notification, which then expands the Output pane and displays error details.
Note
TMDL view modifies only the semantic model metadata, without refreshing data or affecting the report. If your changes require a data refresh, such as altering a PowerQuery expression or calculated column expression, you must manually refresh the table or model for the changes to take effect. Additionally, renaming a field in TMDL view may break visuals within the report that use that field.
In TMDL view you can have multiple script tabs at once, any of which can be renamed or removed.
The contents of the TMDL view tabs are saved in the report file when you save the Power BI Desktop report, so you can continue where you left off the next time you open the Power BI Desktop report file. When saving to a Power BI Project (PBIP), each script tab is saved as a .tmdl file in the \TMDLScripts folder, as shown in the following image.
Tip
You can open and edit TMDL scripts in Visual Studio Code, and they will properly reload after restarting Power BI Desktop.
The Problems and Output panes display errors and messages specific to the script tab that's currently selected and displayed. Switching to a different TMDL scrip tab refreshes both of those panes with information specific to the selected and currently shown tab.
You can select the Clear button to empty the Output pane messages.
Messages are kept only for each Power BI Desktop session, so restarting Power BI Desktop clears all output messages for all script tabs.
When you save your work as a Power BI project (PBIP), you gain access to your semantic model definition metadata as TMDL files, providing a useful source control and co-development experience, while also allowing you to make changes to the semantic model outside of Power BI Desktop. However, if you modify the TMDL files within the PBIP, you must restart Power BI Desktop to reload those changes. In contrast, the TMDL view follows a scripting mental model, enabling you to efficiently apply changes directly to the semantic model being edited in Power BI Desktop using TMDL, regardless of whether the file format is PBIX or PBIP.
You can seamlessly integrate both experiences. For instance, you can update the TMDL definition in PBIP for quick changes without launching Power BI Desktop, and utilize the TMDL view when Power BI Desktop is already open to efficiently implement a series of changes to the semantic model using TMDL. Both approaches offer a rich and consistent TMDL coding experience.
Scenario: I need to reuse or share a semantic model table with its complete definition, including columns, Power Query expression, and sort by configuration, and others in another semantic model.
Solution: Open the semantic model with the table, script it using the TMDL view. Copy the script to the other Power BI Desktop window, open the TMDL view tab, and apply the script.
Scenario: I've named all my tables with the prefixes "dim_" or "fact_". I'd like to remove these prefixes without manually updating each of the over 100 tables.
Solution: Open the TMDL view, script the semantic model, search for the prefix (regular expressions are supported) and replace it with an empty text.
Scenario: I need to create a perspective in my semantic model to use the personalized visuals feature. However, I can't create or edit it using the graphical interface of Power BI Desktop.
Solution: Open the TMDL view, create a new empty tab (or use the script from an existing perspective), then create or edit the perspective using TMDL. This method also applies to other semantic model metadata that lack a graphical interface, such as translations, detail row expressions and others.
createOrReplace
perspective SalesView
perspectiveTable Sales
perspectiveMeasure 'Sales Amount'
perspectiveMeasure 'Sales Qty'
perspectiveColumn Quantity
perspectiveColumn 'Amount'
Scenario: I need to modify the Power Query expression of my table without triggering a refresh.
Solution: Script the table, modify the Power Query expression, and apply the changes. TMDL view does not require refreshing your data.
Scenario: I need switch the storage mode of my table from DirectQuery to Import, and vice-versa
Solution: Script the table, update the partition mode, and apply changes.
Scenario: I need to back up my semantic model definition before making significant changes and easily roll back to a previous definition, if needed.
Solution: Script the semantic model or specific parts you want to back up, make your changes in other views, and if needed, return to the TMDL view to restore the previous metadata by running the saved script.
TMDL view is currently in preview, so keep the following limitations in mind:
The following articles describe more about TMDL and its uses.
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