As Power BI models become increasingly complex and mission-critical, development teams need more control, visibility, and collaboration capabilities. That’s where TMDL View (Tabular Model Definition Language) comes in a recent Power BI Desktop feature that gives users direct access to the underlying structure of semantic models. It provides a readable format that makes it easier to explore, understand, edit, and manage the model’s metadata. With TMDL View, it is possible to script tables, measures, and other model objects. Whether managing a large-scale enterprise model or collaborating across teams, TMDL simplifies version control, boosts productivity, and helps you build more maintainable models. In this article, we explore its top benefits and most powerful use cases.

Why Use TMDL View?

TMDL View introduces a YAML-based scripting interface that enables developers to manage their semantic models in a more code-like manner. Its key benefits are:

• Development Efficiency:

TMDL View code editor supports features such as search-and-replace, keyboard shortcuts, multi-line edits, and more directly inside Power BI.

• Transparency and Control:

Users can view and edit all semantic model objects and properties, including those not accessible through the standard Power BI interface.

• Reusability:

Users can write TMDL scripts once and easily reuse or share them across projects.

TMDL also integrates seamlessly with version control tools like Git, enabling modern CI/CD practices in Power BI development.

Top Use Cases of TMDL View:

TMDL View’s code editor is more than a basic scripting tool – it’s a complete development environment designed to transform the way we work with our semantic models.

The most valuable use cases include:

1. Bulk Editing

• Adding Descriptions
  Enhance model clarity and usability by documenting the purpose of multiple tables, fields and measures through descriptive comments in a single step.

• Find and Replace
  TMDL View allows users to efficiently rename multiple tables, columns and measures at once, eliminating the need for manual updates. By using the find-and-replace functionality, object names across the model or existent errors can be updated in seconds.

• Format Data Types
  With TMDL View, users can define or adjust the data types of columns and measures by specifying properties such as dataType and formatString. This capability ensures consistency across the model.

• Group Measures into Folders Efficiently
  Assign measures into their designated folders in a single action, improving model organisation and navigation.

2. Bulk Measure Creation

• Reusable DAX Code
  With TMDL View, there is no need to rewrite DAX formulas from scratch. Users can copy existing measures, paste them and make the necessary adjustments.

• Migrating semantic model objects
  TMDL View makes it easy to reuse semantic model objects across multiple models, promoting consistency and reducing errors. If the user has a set of commonly used DAX measures, there is no need to recreate them for each model. By copying and pasting the script between models, the objects can be reused.

3. Modify Relationships

Users can easily adjust relationships between tables by making quick edits directly in TMDL View.

4. Edit M-Code, Switch Data Modes, and Adjust Summarization

Users can make direct changes to Power Query M-code with TMDL scripts without having to open the query editor. It is also possible to switch between Import and Direct Query modes using simple TMDL commands and update summarisation settings for multiple columns at once, minimising manual effort.

5. Review Security Roles

Users can quickly inspect all defined security roles—both Row-Level Security (RLS) and Object-Level Security (OLS)—directly within TMDL View.

6. Preview and Validate Changes to the Semantic Model

TMDL View allows users to preview changes before applying them. By showing a side-by-side TMDL code diff, you can compare the semantic model before and after script execution. This is especially useful when copying scripts from external sources, as it allows for an assessment of the impact on the semantic model before making any changes.

Conclusion

TMDL View is a significant advancement in the development and maintenance of semantic models in Power BI. By introducing a human-readable, text-based format (YAML), TMDL simplifies the understanding, editing, and version control of data models. This also facilitates the collaboration between team members.

It aligns well with modern development practices, enabling seamless integration with tools such as Git and supporting continuous integration/continuous deployment (CI/CD) pipelines. Developers gain greater flexibility, traceability, and efficiency when managing complex models while also benefiting from improved collaboration and reusability, which gives users better control.

As Power BI continues to evolve, TMDL is a key enabler of scalability and maintainability, representing a significant step toward scalable, enterprise-grade BI solutions.

References:

https://powerbi.microsoft.com/en-us/blog/deep-dive-into-tmdl-view-for-power-bi-desktop-preview/