Data layer based architecture makes BI platforms more scalable
The below pyramid shows how value is added to raw data with analytics and business intelligence
DWH Platform architecture: Current trends
In the past it has been common to have a single DWH platform throughout the company which would typically include the data visualizing tools. SAP BW, IBM Cognos, Oracle Analytics are examples of such DWH systems.
The new data visualizing tools like Qlik and Tableau are challenging this classic approach which is sometimes also known as "single source of truth". Typical new DWH scenario is a mix of multiple vendors, tools and includes cloud based solutions (SaaS)
...Also there are new database systems available to suit the growing volume and variety of data