Beware the Objection Removers - InformationWeek

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Software // Information Management

Beware the Objection Removers

Is that sales pitch flying in the face of conventional wisdom? Start asking questions now.

You don't need a data warehouse, you can query the source systems directly. This is an old and venerable objection remover that has been around since the earliest days of data warehousing. Originally, it was easy to disqualify this objection remover because the source transaction systems didn't have the computing capacity to respond to complex end-user queries. But with the recent technical advances in grid computing and in powerful, parallel-processing hardware, a good salesperson can argue that the source systems do have the capacity to do the double duty of processing transactions and serving end-user queries. But in this case there's a larger issue: The data warehouse is the comprehensive historical repository for perhaps your most important company asset—your data. The data warehouse is purpose-built to house, protect and expose your historical data. Certainly these issues have come sharply into focus with the recent emphasis on compliance and business transparency. Transaction processing (legacy) systems are virtually never built with the goal of maintaining an accurate historical perspective on your data. For instance, if the transaction system ever modifies a data element by destructively overwriting it, you've lost historical context. You must have a copy of the transaction system because the historical context is structurally different from the volatile data in a transaction system. Thus, you must have a data warehouse.

You can leave your data in a normalized structure all the way to the end users. The larger issue: Support systems will only work if they seem simple to the end users. Building a simple view is hard work that requires very specific design steps. In many ways, the delivery of data to the end users and their BI tools is analogous to the final delivery made by a restaurant chef from the kitchen through the door to the customers in the dining room. We all recognize the contribution made by the chef in making sure the food is perfect just as it's being taken from the kitchen. The transfer of an (uncooked) complex database schema to end users and their immediate application support specialists is in some ways worse than an objection remover: It's a snare and a delusion. To make this work, all the transformations necessary to create a simple view of the data are still required, but the work has been transferred out of IT to the end user. Finally, if the simple data views are implemented as relational database "views," then the simple queries all devolve into extremely complex SQL that requires an oversized machine to process!

Applications integrators make incompatible legacy systems smoothly function together. The larger issue: Incompatibilities don't come from deficiencies in any technology, but rather from the underlying business practices and business rules that create the incompatible data in the first place. For any application integration technology to work, a lot of hard work must take place up front, defining new business practices and business rules. This hard work is mostly people sitting around a table hammering out those practices and rules, getting executive support for the "business process reengineering" that must be adopted across the organization and then manually creating the database links and transformations that make an integrated system work.

A centralized customer management system makes your customer data issues go away. This is a subtle objection remover that's not as blatant as the first three. Probably every company would benefit from a rational single view of their customers. But only a core part of the customer identity should be centralized. Once a single customer ID has been created and deployed through all customer-facing processes, and selected customer attributes have been standardized, there remain many aspects of the customer that should be collected and maintained by individual systems. In most cases, these systems are located remotely from a centralized site. For example, in a bank, specific behavior scores for credit-card usage are rarely good candidates for transferring to the central customer repository.

You don't need to build aggregates. The larger issue: Data warehouse queries typically summarize large amounts of data, which implies a lot of disk activity. Supporting a data warehouse requires that you constantly monitor patterns of queries and respond with all the technical tools possible to improve performance. The best ways to improve query performance in data warehouse applications, in order of effectiveness, have proven to be 1) clever software techniques building indexes on the data, 2) aggregates and aggregate navigation, 3) large amounts of RAM, 4) fast disk drives and 5) hardware parallelism. Software beats hardware every time. The vendors that talk down aggregates are hardware vendors that want you to improve the performance of slow queries on their massive, expensive hardware. Aggregates, including materialized views, occupy an important place in the overall portfolio of techniques for improving performance of long-running queries. They should be used in combination with all the software and hardware techniques to improve performance.

Leave all your security concerns to the IT security team. The larger issue: Data warehouse security can only be administered by simultaneously being aware of data content and the appropriate user roles entitled to use that data. The only staff who understands both these domains is the data warehouse staff. Controlling data security is a fundamental and unavoidable responsibility of the data warehouse team.

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