设计数据仓库的注意事项(Part II)

End Users

The end users are who you are designing and building the data warehouse for ?your customers. They rely on the information they extract from the warehouse in order to work more effectively and efficiently. They also ultimately determine whether or not your data warehouse project met its stated goals. For these reasons, your project must be built around providing the end users with the information they need in a user- friendly fashion.

The primary end users for data warehouse information are report recipients and query designers. They provide the results of their work to the decision makers who determine the course of your organization.

Report Recipients

Report recipients are the end users most dependent upon the information extracted from the data warehouse. They include business analysts, financial analysts, mid-level managers, senior managers and executives. Although some of the report recipients will have participated in the design process, they will have different perspectives as end users. They will have the greatest interests in report content format and requirements, time frame and update frequency, ad hoc query capabilities and drill down/drill through requirements.

Report content and format requirements define what information is presented and arranged. Your end users will each have a special perspective on what information is important in the periodic reports they rely on. Many times they will need similar source data, but the reports will contain different calculated values and extrapolations. Even when they agree on what information must be present, they each have a different set of requirements when it comes to how the information is arranged. Each of these views must be taken into consideration when defining your project requirements.

Query Designers

Query designers are technically competent people who are tasked with building the queries that provide the reports. They have to please the report recipients while working under those limitations imposed by the structure and content of the data warehouse.

The query designers are a valuable resource in the same areas as those represented by the report recipients, but from a different perspective. They frequently ask you to include calculated columns the report recipients don抰 know are necessary. They also ask for simpler structure in many areas, so as to make their query designs more manageable and also demand highly denormalized tables wherever possible.

Management

Management will typically provide the most demanding and least detailed set of requirements from the data warehouse project. You can expect such requests as, "I need to know how profitable we are on a quarterly basis." or "Who are our top 100 customers?" You will then have to work to define profitability and top customer in terms that can be applied to the data warehouse.

Management requirements usually fall into three general categories: strategic reporting and projections, tactical reporting and enterprise standards compliance.

Strategic Reporting and Projections

Strategic reporting and projection are long term processes aimed at positioning the organization to remain competitive in the marketplace. Strategy is defined as a plan designed to place an organization in an advantageous position prior to competition. From this we can see that the information needed to support strategic initiatives concerns long-term trend and market p.netration analysis, long-term raw material inventory availability and usage, changes in the technical environment, work force projections and customer demographic information. Each management team will have its own list of specific information they need in order to help them formulate or adjust the corporate strategy.

Tactical Reporting

Tactical reporting deals with understanding how day-to-day operations are meeting strategic objectives. These short-term reports may consist of daily, weekly, monthly, quarterly or annual analyses of the current state of affairs within the organization. These reports will contain operational information on sales statistics, workforce utilization, inventory management and measures specific to each industry. The timeliness of these reports requires information be made available as rapidly as possible after it is captured. It is not unusual for management to require that daily reports be available when they arrive for work on the following day, or that weekly reports be available by 9:00 AM on Monday morning. Your data warehouse will have to be tuned to provide the required levels of performance.

Enterprise Standards Compliance

Enterprise standards compliance consists of insuring that all parts of the organization are working in the aclearcase/" target="_blank" >ccepted manner. The reports that help management determine the extent to which this is true can range from very simple, with only a few rows, each containing only four or five columns, to complex, multi-page reports, supported by pivot tables and charts. The extent to which your management team wishes to track standards compliance will effect the level of detail that you will need to capture. For instance, should the management team want to insure that each workgroup is complying with corporate standards regarding work hours and break times, your warehouse will have to contain all the pertinent data on each employee抯 schedule over a specified period of time. You will also have to build summary tables to support more general analyses.

Systems Staff

Your systems staff members will help identify the best hardware, software and connectivity configurations for your warehousing operation. They also will help you identify the risks and limitations presented by each possible configuration.

Hardware

Hardware consists of all the processing, storage and peripheral components upon which your data warehouse operation will reside. Your systems specialists will help you make intelligent and informed choices regarding mainframe, mid-range, mini-computer or personal computer processing; multiple processing, either parallel or distributed; distributed or concentrated storage; and all the decisions that determine the physical structure of your warehouse environment.

Operating System and Software

In some cases, the operating system (OS) and software choices available to you will be determined by your hardware selections. In other cases, the hardware choices will affect, but not dictate, the OS and software options available to you. Your systems specialists will work with you to determine which combinations fit your project抯 needs while complying with corporate standards.

Connectivity

Connectivity deals with all the components and associated communications that allow one computer to send and receive information from another. Your system team members will provide you with valuable information regarding the choices available, recommended configurations, currently implemented designs and any enterprise standards your project must comply to.

Security Staff

Your organization抯 security specialists fall into two main categories, information/systems security and facility/physical security. In each case, these specialists will provide your team with information vital to the success of your project.

Information/System Security

Information and system security issues center on three primary categories: authentication, authorization and use control.

Authentication is the process of insuring that a particular individual is accurately identified. Authorization deals with those mechanisms that prevent a person from gaining access to applications or databases they should not have access to, while insuring access to applications or databases they has obtained approval for. Use control is concerned with limiting each individual to operations that have been identified as appropriate for their job and operational functions.

Facility/Physical Security

Facility and physical security issues are concerned with where and when particular individuals may be in corporate properties, what they can do while there and making sure corporate property is secured against malicious damage and theft. Three of the categories of facility and physical security are the same as those for information and system security: authentication, authorization and use control as well as loss prevention.

As is the case with information and system security, authentication is the process of insuring that an individual is, in fact, who they purport to be. Authorization concerns the process of allowing only those with the proper clearances to enter specific areas within corporate facilities, while providing complete and ready access for those who should be there. Use control deals with insuring each facility or physical structure is used in accordance with corporate policy, and those present comply with all safety and regulatory requirements. Loss prevention involves protecting both corporate and personal property from theft or loss through other means (fire, vandalism, etc.), as well as providing for the safety of those individuals who are working at or visiting at the facility.

Physical Maintenance Staff

The physical maintenance staff ?janitors, plumbers, electricians and facilities planners ?can provide additional information to your project team. Although this group is seldom included in project requirements planning sessions, their input can be essential.

Facilities

Assessing the facilities available to your project team for the design and development phases, as well as identifying the physical locations for hardware and for the long-term warehouse operations team are vital to insuring the project can be completed.

If you are unable to find workspace and meeting rooms for your team members, the project will be delayed at best. If you fail to identify the room in which your database server will be located ?and reserve the required space and utilities as soon as possible ?you may find yourself with a complete project plan and excellent design documentation, but with no place to set the hardware.

You will also need to verify that team members can access, both physically and through telecommunications, the various locations associated with your project. They also need to know the dates and times access is valid for each facility, and what, if any, prior notifications and approvals are necessary.

For each of the involved facilities, you need at least some participation from personnel assigned to that facility, primarily the facilities maintenance staff. These are the people who can best advise you on those factors that will limit your options in this respect.

Maintenance Schedules

The facilities maintenance teams will also be able to advise your team as to scheduled maintenance activities that will affect your project schedule. Such maintenance activities include: new construction, repairs, telecommunications updates, power grid maintenance and large scale personnel relocations.

The facilities team members will also be able to advise your project team on estimated down times for unscheduled maintenance activities. These activities are typically associated with external problems completely outside the control of your organization. Your organization will most likely have a plan in place for the restoration of services should any such problem occur. This is the information that the facilities team members can provide and thus save your team the effort of reconstructing the supporting estimates and disaster recovery plans.