Now that you have a first draft of the model, what do you need to do to complete it?
Start by reviewing each individual question or issue that has been logged. Many questions that seemed big are easy to resolve now that the rest of the model has taken shape. As you continue your review, the remaining questions tend to fall into three broad categories. The first group requires further research to understand the topic or element. This research is often divided among team members. While some of this is systems research, some requires interaction with the business community to understand how the business works. Many times, this research results in obvious modifications or enhancements to the model. However, sometimes this new understanding puts the issue into the next category.
The second group is where we understand both the user needs and the data we have, but we need to determine how to model it properly. Different alternatives may be explored. Sometimes these questions simply require giving the modeler time to think about the issue.
The third group of issues can be the most challenging because they involve business decisions. Many topics require the business community to examine differences between various parts of the organization (e.g., how business is accounted for literally in the general ledger). This project may be the first time that different groups have needed to face these issues. Often, the problems have existed for years, but have not been visible and/or have been ignored. Resolution of business policy issues takes much longer than resolution of the other types of issues.
The team needs to split up, conduct research and then reconvene to review progress. Work from top to bottom of the issue log each time, keeping notes about research results and decisions made. Many times I include interesting or controversial topics in the issue log noted as information only or as a topic having an impact on the extract, transform and load (ETL) process. This captures helpful background information.
Bring in the true business perspective before you get too far along. Typically several iterations into the model, we bring in to one or two businesspeople. These people should be carefully chosen and be patient, tolerant of change and willing to work with you.
I have found the most effective method of presenting the business dimensional model to business users is with overhead transparencies. You need to introduce the concepts of facts and dimensions, and explain the diagramming technique. Then, walk through a realistic business scenario. For an education example, use the school district dimension to select a specific district. Next, use the period dimension to constrain which school year to include on the report. Also, select the student test of interest, perhaps the fourth-grade reading test. Finally, select the number of students passing fact from the Student Achievement Test fact group. This gives the business users a good understanding of how the dimensional model works. Walk through the entire model in detail, starting with the dimensions. This is painstaking but necessary.
Using transparencies allows you to make changes in a manner that everyone can immediately see. Continue to keep up with all the documentation. Electronically make changes to the model during each review session. Keep track of new issues, comments and resolution of any issues.
Continue working on the issue log, revising the model and conducting business reviews until you have addressed all of the issues. As you work through the remaining open issues, topics that are far outside the scope for the initial implementation may be deemed issues to be addressed in the future if this is agreeable to the entire project team, including the business representative(s).
When changes to the model are minor tweaks rather than drastic revisions, the model is nearly complete. New business questions or challenges are easily met by walking through the model. As one final cross check, I like to review each source data element to make sure that it is either placed in a dimension or fact group, or we have determined that it is operational only and will not be included.
A final walk-through of the model should include everyone who participated in gathering requirements. The format of the meeting is the same as the previous business reviews with one significant difference the business representatives who have participated in previous reviews should assist with the discussion of the model. When you have hit the model on the head, the users will be pleased but somewhat under-whelmed do not let this disappoint you. This means your hard work has paid off. This is supposed to be an intuitive business view of the data so it should make sense and seem almost obvious to them. Celebrate this success!
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