I spent a good bit of time looking for the definitions/descriptions of the TMSCHEMA DMVs that allow us to view metadata and monitor the health of SSAS 2016 tabular models. As far as I can tell there are no details about them on any Microsoft site. Many of the columns are obvious, but there are a few fields that show IDs rather than descriptions (e.g., ExplicitDataType in TMSCHEMA_COLUMNS, Type in TMSCHEMA_DATA_SOURCES). It would be great to get the DMVs documented similar to the MDSCHEMA DMVs as they are quite useful for tasks like documenting your tabular model. Since the TMSCHEMA DMVs work in Azure Analysis Services as well, I have logged this request on the Azure AS User Voice for that. Please lend me a vote so we can make this information more easily available.
Please Lend Me Your Vote for Documentation of TMSCHEMA DMVs
Data Savvy 
Along a similar vein, I have logged two Power BI ideas (as TMSCHEMA DMVs work in Power BI as well).
1) Provide a GUI to browse DAX calculations, so you can get a view of all calculations in your model in one place
https://ideas.powerbi.com/forums/265200-power-bi-ideas/suggestions/17030470-provide-a-gui-to-browse-dax-calculations
2) View model metadata (tables, relationships, columns, measures) for all models across a tenant in the Power BI server
https://ideas.powerbi.com/forums/265200-power-bi-ideas/suggestions/17030698-view-model-metadata-tables-relationships-column
Your support is appreciated.
Hi Meagan. I am also eagerly awaiting some official documentation on these DMVs. I have upvoted on UserVoice, fingers crossed.
In the meantime, I don’t suppose you have the decodes for the ExplicitDataType and InferredDataType in the Columns DMV do you?