When is this a problem?
All sources of data should either be a file or module view, not a list or module.
Why is this a problem?
When using a list or module as a data source, there are no filtering mechanisms available.
How to correct:
It is a recommended best practice to use a saved view when importing data from one model to another, especially for data loads that are repeated or updated frequently as part of an action or process. See the lessons Filtering Best Practices and Saved Views for Importing for more information. You may want to rename the saved view source to reflect what the saved view represents.
Filtering Best Practices
Saved Views for Importing
Data Hubs: Purpose and Peak Performance
Questions on this topic? See Check the data sources. Are some of them lists or modules? in our Model Optimization Checklist forum.