| The central metadata repository contains an enterprise-wide view of the data. The repository organizes this metadata into a data model whose scope encompasses the entire organization. We call this the EDM. The EDM provides a schema or blueprint of the organization's business. In the previous section, we discussed how metadata provides the context for data. When the context encompasses the entire organization, it describes the organization's business. To achieve this end, the EDM is a compilation of metadata from all systems within the organization. This is shown in Figure 10.5. Figure 10.5. Enterprise data model.  As shown in the diagram, each department provides its own input into the EDM. The departments need to provide complete metadata for each system. The data administrator integrates this information into the EDM. The challenge for any system that spans departments is reaching a consensus. There will be disagreements concerning the data's definition, attributes, and business rules. Virtually all the metadata elements have the potential of becoming hotly contested issues. The only real blessing for the data warehouse architect is that this is not his or her responsibility. It is the responsibility of the data administrator. Actually, in shifting the responsibility to the data administrator, I am only half joking. Strictly speaking, the EDM is not part of the data warehouse project any more than it is for the implementation of any other system. It is often confused as being part of the warehouse because the warehouse is the first system that truly attempts to integrate the data from the disparate operational systems. As shown in the diagram, the data warehouse not only contributes to the EDM, but receives input from it as well. While in a perfect world new systems would be designed with consistent metadata, in reality this is rarely the case. Most often, departments purchase systems from multiple vendors by selecting the best of breed. As of this writing, vendors have not done us the courtesy of providing a standard set of metadata. While the EDM is not part of the data warehouse, it is most definitely part of the IEBI system. Understanding the need for quality metadata in an IEBI environment places the EDM squarely in the center of IEBI. As such, we need to understand the necessity to construct a central metadata repository that has as complete a view of the entire organization as is practically possible. |
