Thanks for the questions.
Right now the cross dataset query interface only supports AND statements among core terms. OR statements are available for the options provided for a core term or the variables mapped to a core term. Including OR statements among core terms is not a technical issue, but might cause confusion or difficulty to novice users. Indeed, this is a balance between simplicity and complexity of the interface.
I am able to get the "combined" count within a single dataset using the example you provided, and cannot reproduce the issue. Please try again and let me know if you still experience such issues.
The new Physio-MIMI cross dataset query interface for NSRR is available on https://informatics.case.edu. The goal of the interface is to be directly used by sleep researchers, for activities across multiple datasets such as data exploration for deriving new hypotheses as well as for cohort identification. There are two main features:
Query Builder, which provides dynamic construction of advanced cross-cohort queries, with terminology support and visual controls such as slider bar, radio buttons, and checkboxes;
Query Manager, which allows for storing and labeling queries for reuse.
If you have any questions or suggestions, please contact us at firstname.lastname@example.org. We look forward to hearing from you so that we can provide more interface features and improve the interface usability. Thanks!