DirectQuery and real-time solutions
The ability to routinely process data with SQL Server Agent (see the Processing the data recipe) gives the model designer a large degree of flexibility to determine when data in the model is refreshed. In fact, the standard practice for Business Intelligence solutions is that data is updated on a nightly basis and therefore model processing becomes part of the nightly refresh.
However, where the source data is rapidly changing, there may be a requirement to implement a DirectQuery solution. This is an environment that is conceptually similar to Relational Online Analytical Processing (ROLAP). Here, the model passes all queries through to the relational database (rather than querying its own data store).
A DirectQuery solution may seem like an extremely attractive option for real-time data access since the model is essentially a semantic definition used to define the model structure. Further, there is no requirement for the model to process data since all...