The best replacement for business rules is requirements.

The best alternatives to business rules are rated as following:
★★★★★  requirements
★★★★  functional requirements
★★★  business requirements
★★★  validation rules
★★★  workflow
★★  acceptance criteria
★★  business logic
★★  business process
★★  calc scripts
★  system rules
★  calculation manager
★  complex event processing
★  use cases
  user stories

Your alternative for business rules is not listed? Suggest!
Speaking about business rules, one probably shouldn't forget about erd.

Other search terms related to business rules and their ratings are:
★★★★★ erd
You have in mind a companion for business rules and it is not yet here? Propose!



Google Trends

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business rules
requirements
functional requirements