I didn't make this clear in my original comment, but I was envisioning that an app like Salesforce would use its own schema, but still live in the same DB with

I didn't make this clear in my original comment, but I was envisioning that an app like Salesforce would use its own schema, but still live in the same DB with other schemas. I'm going to assume that Salesforce has some notion of an Employee. Salesforce would use its own Employee table by default, but it would provide extension points (views and SPs) that would allow you to read and write Employee data from tables in another schema if you want. This might be preferable to duplicating Employee data. Edit - I just saw that you addressed this in your original post: "nobody offered applications that could be configured to an existing data base"