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Data modelers workbench - Hoberman S.

Hoberman S. Data modelers workbench - Wiley publishing , 2002. - 495 p.
ISBN 0-471-11175-9
Download (direct link): datamodeler'sworkbench2002.pdf
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14. Logical Data Modeling Create a normalized logical data model Normalization Hike 8
15. Apply abstraction Abstraction Safety Guide Abstraction Components 9
Table 4.3 (Continued)
16. Appropriately arrange logical data model Logical Data Element Sequence Tips Entity Layout Tips Relationship Layout Tips Attention-Getting Tips 10
17. Physical Data Modeling Denormalize the logical into a physical design Denormalization Survival Guide 8
18. Appropriately arrange physical data model Physical Data Element Sequence Tips 10
Tools to Help with This Task
The two tools to help with this task are the Data Modeling Phase Tool and the Phase-to-Task-to-Tools, which represent a large portion of this chapter. The Data Modeling Phase Tool is a handy list of the data modeling phases and how they correspond with the life cycle phases during project development. The Phase-to-Task-to-Tools describes the tasks and tools associated with each phase.
Create Data Modeling Estimates for Project Plan
The chapter on creating data modeling estimates is also about the estimating approach. How long will each task take? This can be a very tricky task because there is a high probability that the project manager, and other individuals with a stake in the cost and overall timeline of the project, might try to influence you. Focus on the facts, and come up with a reasonable effort based on your experience and the tools provided in this chapter. Keep in mind that in many cases your estimate will have to be changed, most likely to fewer days. Thus, in coming up with this estimate, also keep in the back of your mind where you might be able to cut corners without much sacrifice to save time. Very rarely is the first estimate the only one. Be flexible without compromising your deliverables.
Tools to Help with This Task
This section on tools to help with this task has two tools to help with estimating: the Priorities Triangle and Good Guess Estimating Tool. Each depends heavily on the Data Modeling Phase Tool and the Phase-to-Task-to-Tools. The Priorities Triangle basically says that you can never have all three: very high quality, minimum amount of time, and minimum cost. At least one will need to be sacrificed. For example, if you want your project done in very little time and costing very little money, the end result usually will be very little quality.
The Good Guess Estimating Tool contains two smaller tools: the Subject Area Effort Range and Task Effort Tool. The Subject Area Effort Range provides the short, long, and average length of time it would take to complete a subject area in days. What is meant by short, long, and average is determined mainly by how much high-quality information is provided to the data modeler and how experienced the entire project team is, including the data modeler. If you are new to estimating or are not sure of the quality of information available for the project, always err on the side of caution. This translates into selecting an average-to-high amount of time for the subject area. Examples of subject areas are Customer, Account, Product, and so on. The Task Effort Tool takes the tasks we have come up with and assigns each a percentage. Multiplying the number of days per subject area by task percentage gives us the amount of time in days to complete the task by subject area. If we are requested to provide effort at the project level instead of the subject area level, then simply get a total number of days for all subject areas (sum up all subject areas) and multiply by the percentage for each task. We will go through an example of applying these formulas shortly.
Subject Area Analysis
The subject area analysis phase contains all of the tasks at the subject area level of detail.
Identify Subject Areas Affected by Application
The first step in starting the subject area analysis is to generate a list of the subject areas that are required for your project, including names and definitions. You need to get agreement and commitment on what each subject area means before data requirements work can get to any level of detail. Also, make sure you are using the appropriate names for each subject area. For example, if the business refers to a Customer as a Client, use Client as the name for this subject area. For this reason, you might break down this task into two smaller tasks: first identify the subject areas based on the terminology of the user and then translate the project-specific subject area names and definitions into corporatewide standards.
Tools to Help with This Task
The Subject Area Checklist provides a starting point to generate the list of subject areas you need for your subject area model. If you do not have much information to start with, or need to encourage project and business teams to get out from the weeds (meaning they are talking at too detailed a level for this point in the project), this tool provides a list of subject areas with generic definitions as your starting point. Work with the team to choose from this list those subject areas relevant to the project. If the resources you are working with disagree with a name or a definition, that is good. This list of subject areas and definitions is provided as a starting point for discussion. Disagreements are good. Document any differences between what the resources say it should be and the standard definition, and work with experts in the subject area to agree on the correct definition or name. There could even be more than one definition
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