40 lines
2.6 KiB
Markdown
40 lines
2.6 KiB
Markdown
# Decision Tables
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DMN tables are powerful tools for modeling and implementing business rules and decision logic.
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They allow you to define rules and their associated conditions and actions in a structured manner.
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By evaluating the conditions in each rule, the DMN engine can determine which rules are triggered based on the provided inputs and execute the corresponding actions.
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This provides a flexible and configurable approach to decision-making in various scenarios.
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A DMN (Decision Model and Notation) table consists of several components that help define the decision logic and structure the decision-making process.
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The main components of a DMN table are:
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## DMN Components
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- ***Input Variables:*** These are the variables that represent the information or data used as input for the decision.
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Each input variable is typically represented as a column in the table.
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Multiple columns represent multiple input variables.
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- ***Conditions:*** Conditions specify the criteria or constraints that need to be evaluated for each input variable.
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They define the rules or expressions that determine when a particular decision rule should be triggered.
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Conditions are usually represented in the "When" column of the table.
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- ***Actions or Expressions:*** Actions or expressions define the operations or calculations that are executed when a specific rule is triggered.
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They represent the logic associated with the decision outcome and are represented in the same row as the conditions in the table.
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- ***Decision Rules:*** Decision rules are the individual rows in the DMN table.
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Each rule represents a specific combination of conditions and actions that define the behavior or logic for a particular scenario.
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Decision rules combine the input conditions and output actions in a structured manner.
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- ***Hit Policy:*** The hit policy determines how the decision engine selects or combines the applicable decision rules when multiple rules are triggered.
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It defines the behavior for resolving conflicts or overlaps between rules.
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Common hit policies include "First," "Unique," "Priority," "Any," and "Collect."
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## Hit Policy
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**Unique:** Only one rule can match the given inputs.
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If multiple rules match, it results in an error or an undefined outcome.
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This policy ensures that only one result is produced.
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**First:** The first rule that matches the inputs is selected, and its corresponding output is returned.
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Other matching rules are ignored.
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This policy is useful when you want to prioritize the order of rules.
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**Collect:** All rules that match the inputs are selected, and the outputs from those rules are collected and returned as a list or a collection.
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This policy allows for gathering multiple results.
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