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February 1, 2003

To Be or Not To Be Centralized

Contrary to conventional data warehouse wisdom, physical centralization is not the question

by Margy Ross
Edited by Ralph Kimball

Continued from Page 1

As I warned earlier, physical centralization without integration may only throw more fuel on the fire of preexisting problems. Management may be convinced that buying a new platform to house the myriad existing data marts and warehouses will deliver operational efficiency and performance enhancements. Depending on the budget, these largely IT-centric benefits might be realized. However, they're insignificant compared to the business potential from truly integrated data. Physical centralization without data integration and semantic consistency will distract an organization from focusing on the real crux of the problem. Inconsistent data will continue to flummox the organization's decision-making ability.

Be Not Afraid Of Greatness

Moving to an enterprise data warehouse bus architecture will of course require organizational willpower and the allocation of scarce resources. No one said it would be easy. The issues brought to the surface when establishing a bus architecture are the generic, unavoidable issues all organizations face when trying to build an integrated view of their data.

Let's examine some of the typical activities involved in migrating disparate data to a bus architecture with conformed dimensions. Of course, since each organization's preexisting environment varies, you'll need to modify these steps to reflect your specific scenario.

Step 1: Identify the existing data marts/warehouses in your organization, as well as those under development. You'll probably be surprised by the sheer number lurking in nooks and crannies. (And don't forget the data cubes sitting on your analysts' desktops.) Note the level of detail (grain) for the data in each of these existing data warehouse deliverables, as well as the inevitable data overlaps. Overlaps in the descriptions of entities will drive the design of conformed dimensions, while overlaps in the calculation of metrics will drive the design of conformed facts.

Step 2: Understand the organization's unmet business requirements for the data warehouse at a high level. Although the enterprise bus architecture needs to keep an eye on the outer boundaries of future data requirements in your organization, the initial implementation must practically focus on the most urgently needed data.

Step 3: Gather key stakeholders to develop a preliminary enterprise data warehouse bus matrix for your organization. These stakeholders include backroom DBAs and source system experts, as well as front-room business analysts. The first stakeholder meeting should be kicked off by a senior executive of the organization who stresses the business importance of reaching agreement on the conformed dimensions and facts. (Then the executive can leave!) Senior-level business commitment is critical to moving beyond the inevitable organizational obstacles.

Step 4: Identify a dimension authority or stewardship committee for each dimension to be conformed and subsequently released to the community. Design the core conformed dimensions by integrating and reconciling the existing, disparate dimension attributes. Realistically, it may be overwhelming to get everyone to agree on every attribute, but don't let that bring this process to a crashing halt. You've got to start walking down the path toward integration in order to gain organizationwide agreement and final sign-off on the master conformed dimensions.

Step 5: Devise realistic, incremental development and administration plans for implementing and deploying or converting to the new conformed dimensions. Ultimately, the conformed dimensions should be used across all data sources to which they connect; however, you can't expect to get there in one fell swoop.

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All's Well That Ends Well

These steps focus on the true, core issues of achieving logical integration across your data warehouse. Formulating the bus architecture and deploying conformed dimensions will result in a comprehensive data warehouse for your organization that's integrated, consistent, legible, and well performing. You'll be able to add data naturally, with confidence that it will integrate with existing data.

Of course, you have the option to implement either a physically distributed system or a classic hardware-centralized system. In both cases, using the enterprise bus architecture and conformed dimensions, you'll deliver integrated business results to your users, which is the whole point of a data warehouse. Your organization's decision-making capabilities will be turbo-charged with consistent data, rather than diverting inordinate attention to data inconsistencies and reconciliations.

Margy Ross [mross@decisionworks.com] is president of DecisionWorks Consulting Inc. and cowrote The Data Warehouse Lifecycle Toolkit (Wiley, 1998) and The Data Warehouse Toolkit, 2nd Edition (Wiley, 2002) with Ralph Kimball.