Decision Modeling

Marlon Dumas Institute of Computer Science

Actions/ Outcomes

Conditions

Each column represents a condition-action rule

Classic Decision tables

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1 2 3 4 5

Leave 8am 9am 9am 10am 10am

Stall? - - - Y N

Accident - Y N - -

Long Medium Long Long Short

DMN – Decision Model & Notation

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}  OMG standard decision modeling notation }  Includes:

}  High-level diagrams to denote decisions, sub-decisions, inputs and knowledge sources

}  Decision tables (a bit different from classical decision tables)

}  Supported by several tools }  IBM ILOG Jrules }  OpenRules }  Signavio }  GenMyModel

Decision Requirements Diagram

© Signavio 2015

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Decision

Sub-decision

Input

Knowledge source

DMN Decision Table

© Signavio 2015

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U

Inputs Output(s)

DMN Decision Table

© Signavio 2015

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U

Decision tables: Numerical ranges

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Incomplete tables and contradictory rules

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•  No rule for Age = Child, Marital status = Not married, Parental status = No kids

•  Rules 1 and 3, and rules 2 and 3 are contradictory

Hit Policies

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}  Unique (single) – the rules are assumed to be non-overlapping so only one rule can fire for a given input

Unique-hit DMN table

© Signavio 9

Hit Policies

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}  Unique – the rules are assumed to be non-overlapping so only one rule can fire for a given input

}  Any – rules may overlap, but if two rules overlap, they have the same output, so any of them can be fired

Any-hit decision table

© Visionalysis 11

Hit Policies

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}  Unique – the rules are assumed to be non-overlapping so only one rule can fire for a given input

}  Any – rules may overlap, but if two rules overlap, they have the same output, so any of them can be fired

}  Priority/first – rules may overlap and/or contradict. In case of overlap, the first rule matching the input is fired }  NOT RECOMMENDED

Hit Policies

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}  Unique – the rules are assumed to be non-overlapping so only one rule can fire for a given input

}  Any – rules may overlap, but if two rules overlap, they have the same output, so any of them can be fired

}  Priority/first – rules may overlap and/or contradict. In case of overlap, the first rule matching the input is fired }  NOT RECOMMENDED

}  Multi-hit – rules may overlap; all rules that can fire for a given input will fire. Their outputs is combined using an aggregation function: }  E.g. max, min, avg, sum

Multi-hit DMN table

© OpenRules (DMN Live Primer) 14

Recap

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}  Decision Trees }  Suitable for modeling simple decisions }  Also used when decision tree is auto-generated (e.g. decision

tree learning)

}  Classic decision tables (rules on the columns) }  Come with a methodology for capturing complex decisions

and ensuring rule completeness and non-overlap

}  DMN decision tables (rules on the rows) }  Provide many additional feature to organize decisions more

conveniently