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Rule-based system

As explained in Machine Learning System Design

A rule-based system produces outputs by applying explicitly specified logical or procedural rules rather than learned model parameters.

A rule-based system applies explicit rules to provide stable, predictable outputs when an ML model is unavailable or performing poorly. It can also handle simple cases while the model handles more complex scenarios. section 13.4

Use a rule-based system as part of a fallback plan by defining:

  • The conditions that activate it, such as model unavailability or poor performance. section 13.4
  • The switching method between the ML model and rules: automatic, manual, or hybrid. section 13.4
  • The boundary between simple cases handled by rules and complex cases handled by the model. section 13.4

Fallback during model failure

When the model is unavailable or performs poorly, the system can return a rule-based response instead of failing silently. A hybrid design can reserve rules for simple cases and the ML model for complex ones, though this adds complexity and breakpoints. section 13.4

How Machine Learning System Design covers it

How deep it goes
Describes the fallback role, activation choices, and model-switching plan without explaining rule-engine internals.
Examples
Uses model unavailability, poor performance, simple-case routing, and unacceptable predictions as operational examples.
What it assumes
Assumes an ML model whose availability, performance, or confidence can determine when rules take over.
What you can do after
Operate/configure a fallback that switches between explicit rules and an ML model through automatic, manual, or hybrid activation.
How it connects
Connects rule-based systems with machine learning models, fallbacks, overrides, monitoring, and feature drift.

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This explainer was generated by Manning's knowledge graph from the text of Machine Learning System Design. The section links point to the parts of the book it draws on.