In the Real World: Variations
In the real world, problems are not tidy or well behaved. Except in the most trivial problems, there always seem to be exceptions and variations that are not well organized. They are the “gotchas” that rise up to wreck our finely crafted models.
For example, patients coming to a hospital typically go to the admitting office first. But when there is a life-threatening situation, the patient goes directly to the emergency room before having to go to admitting. These are the variations in the real world, the different special cases that our system has to deal with.
And this is what creates headaches for us analysts. Can patterns help us deal with variation more efficiently?
I have used an approach to make explicit the variations in the system and then use the analysis to identify the patterns I ought to use in my design. The steps in my approach are as follows:
1. |
Identify the most important features in one case and organize them in a matrix. Label each feature with the concept that the feature represents. |
2. |
Proceed through the other cases, expanding the matrix as necessary. Handle each case independently of the others. |
3. |
Expand the Analysis Matrix with new concepts. |
4. |
Use the rows to identify rules. |
5. |
Use the columns to identify specific cases. |
6. |
Identify design patterns from this analysis. |
7. |
Develop a high-level design. |