The Microsoft® Data Warehouse Toolkit: With SQL Server™ 2005 and the Microsoft® Business Intelligence Toolset

13.1. Metadata Basics

One of the most common definitions of metadata we hear is "Metadata is data about data." This is vague to the point of uselessness. It doesn't help you understand what metadata is or why you should care. We think about metadata as all the information that describes the contents, structures, and operations of the DW/BI system. Metadata defines the contents of the warehouse, the structures that hold those contents, and the processes that brought those contents into being. In this section, we talk about the purpose of metadata, describe the common types of metadata found in the DW/BI environment, and discuss the concept of the metadata catalog.

13.1.1. The Purpose of Metadata

Metadata serves two main purposes: defining and describing the objects and processes in a system.

Some metadata is used to define a process, object, or behavior. When you change the metadata, you change the process. A simple example is the start time of a SQL Server Agent job. Change the value of the start time element and you change the start time of the process. This idea of using metadata to define a process outside the code was an early, practical use of metadata. Separating a program's code from its parameters and definitions allows the developer (and in some cases, the user) to change the parameters and definitions without having to edit and recompile the code. This concept has been around for decades in forms like table-driven programs and configuration files. In a similar fashion, ...