Microsoft stresses that writing queries directly against system tables is a bad idea. Microsoft reserves the right to change the underlying definition of system tables, so the correct and safest way to query system data is through a system function, a stored procedure, or one of the ANSI-standard information schema views.
Information schema views are handy, and I use them all the time. However, sometimes I want to see how the information schema views get their information, so I peek under the covers. The information schema views are visible in the master database, just as any other view is.
Reading Microsoft-supplied stored procedures is a great way to learn undocumented tips and cool T-SQL coding tricks. And reading the information schema views is a great way to learn about the inner workings of SQL Server. This exercise might not be quite as exciting as the newest Tom Clancy novel, but it will give you something to do with your free time—as if DBAs have any free time.