I’ve just argued why Microsoft was obliged to include this functionality in SSAS v.next but in fact there are many positive reasons for doing this too. The most obvious one is to do with support for more data sources. At the moment SSAS Tabular supports a pretty good range of data sources, but the world of BI is getting more and more diverse and in order to stay relevant SSAS needs to support far more than it does today. By using Power Query/M as its data access mechanism, SSAS v.next will immediately support a much larger number of data sources and this number is going to keep on growing: any investment that Microsoft or third parties make for Power BI in this area will also benefit SSAS. Also, because Power Query/M can query and fold to more than just relational databases, I suspect that in the future this will allow for DirectQuery connections to many of these non-relational data sources too.
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