Planning a Data Warehouse - System Requirements
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This phase identifies the requirements/functions that the data warehouse will deliver. In addition to the features and functions needed, the requirements will clearly describe the operating environment in which the data warehouse will be delivered.
The amount of requirements gathering depends on the implementation approach that you take. The goal is to get an understanding of the core use of initial data and to identify other users who may need to leverage access to the data.
The primary purpose of collecting end user requirements for a data warehouse is to understand how users conduct their business, what data they currently use, and what they would like to do in the future. You should be able to further break down this information into Business entities and their attributes, relationships between the entities, and hierarchies.
The requirements can be gathered through a series of interviews with the different users. Answers to the following questions from the different users will generate the requirements needed for further development of the data warehouse.
- Executive's/Owner's Requirements:
- Why are we building a data warehouse? What business problem will it address?
- How much will it cost?
- When will it be ready?
- What is the impact on people? Skills? Organization?
- What does it do to our current computer investment?
- Do we have the skills to do it?
- What are the risks?
- Architect's Requirements:
The architect views the data warehouse in the abstract and lays out its various components.
- What analyses do you wish you could get more frequently?
- What functions and features will be offered?
- What platforms are needed for implementation?
- How will standards and open interfaces be used?
- How much flexibility is there for adding enhancements?
- Developer's Requirements:
The developer views the warehouse in more specific detailed terms. - Request a further break down of the Architect's requirements into specific applications, interfaces, computers, databases, communication protocols, and user-interface screens.
- What are the Deployment Requirements?
- Access and delivery methods?
- Access tools?
- Connectivity requirements?
- Client Platform requirements?
- End User Requirements:
- How does the data warehouse's functionality fit the end user's daily workflow?
- What are your Query Requirements?
- What types of ad hoc analysis do you do?
- What level of detail is included?
- What are your reporting requirements?
- What reports do you create?
- How often do you perform this analysis?
- Who gets the information?
- How is it used?
- Where do you get the information from?
- At the end of each interview, ask each candidate to develop a wish list which would include things that you would want to be able to do if there were no financial or time or technical constraints in your way. Next we develop a cost requirement.
Cost Requirements:
Traditional cost assessment is not applicable in developing a data warehouse because it uses an iterative development process, therefore making it impossible to predict end-user's summaries and changes.
However, project managers can determine percentages and priorities of work involved in the development. A percentage of at least 10% should be allocated to metadata management throughout the life-cycle of the warehouse.
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