https://github.com/navikt/fp-nare

NARE - Not A Rule Engine
https://github.com/navikt/fp-nare

backend bibliotek familie felles foreldrepenger nare

Last synced: 5 months ago
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NARE - Not A Rule Engine

• Host: GitHub
• URL: https://github.com/navikt/fp-nare
• Owner: navikt
• License: mit
• Created: 2019-03-04T10:38:05.000Z (over 7 years ago)
• Default Branch: master
• Last Pushed: 2026-01-07T13:54:40.000Z (6 months ago)
• Last Synced: 2026-01-14T03:35:36.853Z (5 months ago)
• Topics: backend, bibliotek, familie, felles, foreldrepenger, nare
• Language: Java
• Homepage:
• Size: 686 KB
• Stars: 2
• Watchers: 16
• Forks: 0
• Open Issues: 2
• Metadata Files:
  • Readme: README.md
  • License: LICENSE
  • Codeowners: CODEOWNERS

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# NARE - Not A Rule Engine

NARE a variation of the Specification pattern, as described by Eric Evans & Martin Fowler here: https://martinfowler.com/apsupp/spec.pdf, adapter to handled more complex cases.  

More generally, it is an implementation of an [Expression Tree](https://en.wikipedia.org/wiki/Binary_expression_tree), but one which can support both unary, binary and ternary nodes expressions. 

# Purpose

To model decision trees so they can be visualised, documented, and traced (inputs, outputs, evaluation), for legal and regulatory review. Both the specification of a rule as well as its execution can be documented.

# Features

* Unary expressions:

  - Sequence: Sequence of expressions, result = result from last evaluation.

  - Foreach:  

  - Not

  - Node:  (node computation supplied by implementor) Allows for arbitrary evaluations to be included.

* Binary expressions:

  - And

  - Or

* Ternary expressions:

* - Computational If/Else:  Simple if/then or if/then/else. Returns result from .

* N-ary expressions:

  - Conditional If/Or/Else:  Allows for evaluating only specific subtrees based on a provided condition.

# Rule documentation

The rule specification may be output to Asciidoc using the supplied Javadoc Doclet.  This will output names of parameters and rules to a single asciidoc document, while the trees will be output to a json document as a set of nodes and edges.  The output format in json is the same for both the specification and evaluation trees (except a few evaluation specific parameters), making both suitable for long term storage.

The json output for a graph is fairly easy to graph out using any appropriate graphing library (Vue, D3, etc.) that supports a node/edge layout.

# Examples

See tests for examples 

* Usage example (running a rule): [Rule evaluation example (modrekvote)](https://github.com/navikt/fp-nare/blob/master/core/src/test/java/no/nav/fpsak/nare/specification/modrekvote/ModrekvoteTest.java)

* Specification example : [Rule specification example (modrekvote)](https://github.com/navikt/fp-nare/blob/master/core/src/test/java/no/nav/fpsak/nare/specification/modrekvote/Modrekvote.java)

* Generating documentation example (here using a unit test, can be adapted to whatever): [Doclet example](https://github.com/navikt/fp-nare/blob/master/core/src/test/java/no/nav/fpsak/nare/doc/doclet/RegelmodellDocletTest.java)

# Contact 

* **External**: Raise an issue here on GitHub

* **Internal**: Slack channel #teamforeldrepenger.