A great way to sharpen our analysis and modeling skills is to continuously address real-world scenarios. A scenario along with its solution appears each month in this Design Challenge column. The scenario is first emailed to more than 1,000 Design Challengers and then all responses, including my own, are consolidated and the best appear in this column. If you would like to become a Design Challenger and submit responses, please add your email address at http://www.stevehoberman.com/designchallenge.htm. If you have a challenge you would like our group to tackle, please email me a description of the scenario at firstname.lastname@example.org.
Corine Jansonius's model received the most points (124 points) and, therefore, won the gold medal. My model received 116 points to claim the silver medal. David Hay's model received 108 points to capture the bronze medal. Scores were very close, indicating that many Challengers preferred each of the models.
Gold Medal Winner
Jansonius's top-down layout is shown in Figure 1. She says, "I first learned about the top-down layout from a presentation by Alec Sharp at DAMA several years ago. He suggested that it's helpful to have a 'direction' to your model, e.g., top down, and it's helpful to be consistent, so people know how to read the model ... much like reading a book, it's easier if the text starts at the top of the page."
Figure 1: Top-Down Layout
A Design Challenger noted, "I like the representation of items flowing down toward customer profitability. I also like how geography, time, customer type and product types are somewhat on the same tier with one another, showing a contribution to the bottom line of customer profitability."
Silver Medal Winner
My arrangement of the model is shown in Figure 2. Although I prefer parent entities above child entities (e.g., region above state), the one guideline I apply is to make the heart of a model easily apparent to the reader. Every model has a main entity or group of entities I call the heart, which the rest of the model focuses on. Each section of a very large model can have its own heart. The heart of this model is customer profitability.
Figure 2: Heart of the Model
One Design Challenger mentioned he preferred this layout "because it places customer profitability in the center - implying it is the central focus of this model. All other data supports the customer profitability."
Bronze Medal Winner
David Hay's layout shown in Figure 3 arranges models according to the following rules:
- All "crow's-feet" (the many sides of the relationship) have their toes facing left or to the top.
- No bent lines. An elbow is a symbol that draws the eye to it, adding complexity without adding any semantic meaning.
- Align boxes along one edge, as much as possible.
- Recognize that this is an aesthetic creation. Consider balance, lines, sizes and shapes of entity classes as aesthetic elements.
Figure 3: Immediate Recognition of Purpose
A Design Challenger described his preference for this layout because, "I immediately know the model is about customer profitability. Making the main entity larger helps clarify purpose."
I recommend putting yourself in your audience's shoes while arranging a model. Use some of the guidelines in this column as well as other techniques (e.g., incorporating color) to make your model as readable as possible.
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