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Decision Tree & Directed Acyclic Graph (DAG) RuleMap

This RuleMap compares a decision tree with a directed acyclic graph (DAG). A strict decision tree hierarchy allows one parent per node, while a DAG allows multiple parents per node. The decision tree is commonly used to document business rules. When we presented this diagram at ORF2008, we proposed DAGs as an alternative method for documenting rules for business users. We also recommended that Business Rule Engine (BRE) software vendors incorporate DAGs into their rule engine software to complement their decision tree functionality. fs

In our experience harvesting business rules with subject matter experts, DAGs are just as effective and as easy to understand as decision trees.  For very complex decision trees, a DAG approach helps to simplify complexity by creating a "slim tree" compared to strict decision trees.

Source: The medical rules in this example are based on a presentation or document on decision trees that we found on the Web. I can't remember where it came from; if you know please contact us so we can link to their source page/document. Whoever created these rules did a nice job because this is a very practical and easy to understand example. Their example was for a decision tree only - - we adapted their rules for the diagram above, and we created the equivalent DAG version. We welcome your comments on DAGs vs. decision trees.

This RuleMap was demonstrated at October Rules Fest 2008 in Dallas, TX. 

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