Feb 18, R McFadyen > An approach promoted by Martin Fowler in Analysis Patterns

Feb 18, R McFadyen History - adapted from Analysis Patterns by Martin Fowler Problem: How do we simplify a class model that includes history in associations? Solution: Create a UML stereotype Example: Suppose we are tracking employment history for people companyperson startdate enddate placement There can only be one instance of placement for a given pair of company and person

Feb 18, R McFadyen To correct this, we need to model Date or Time: companyperson startdate enddate placement timeperiod Now, there can be one instance of placement for a given triple of company, person, and time History - adapted from Analysis Patterns by Martin Fowler

Feb 18, R McFadyen This complicates our diagram; there are two class symbols where, perhaps, two will do. This is important in situations where this pattern may be repeatedly used We define/document a stereotype, >: companyperson We define > to represent a solution where an association class is present that carries historical information allowing more than one instance per pair of associated classes. These instances are defined by a start date and end date, and where no two intervals overlap placement > History - adapted from Analysis Patterns by Martin Fowler