Rules that give you too much freedom

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Rules that give you too much freedom

Freedom should be removed by rules. In fact, a rule that does not remove freedom in some way is not a rule according to the SBVR standard. That being said, you may be confused by the title of this column. Well, given this restriction on what a rule is and what you expect from a rule statement, there are still many ways to express such a rule.

RuleSpeak and SBVR’s Structured English impose some restrictions on our use of language (see the box below), but due to the flexible nature of natural language you still have a lot of freedom … consequently, we rarely see the same rule written in exactly the same way by different people using natural language.

There is a tendency to ask for a more restricted rule language to improve:

  • consistency in writing similar rules by different people,
  • consistent interpretation (non-ambiguity),
  • support for validation & verification,
  • translation to software systems.

 

RuleSpeak and SBVR restrictions


Every business rule statement must contain at least one business rule keyword.

The keywords in RuleSpeak are:

  • ‘must’
  • ‘only’

The keywords in SBVR Structured English are:

  • ‘It is obligatory that’
  • ‘It is necessary that’

 

Expressing rules as decision tables or decision trees greatly reduces your freedom of form but also your expressiveness. So, when I need the expressiveness of natural language, I introduce very specific rule patterns to restrict my freedom and gain rigor.

Examples:

  • … must be calculated as ….
  • A … for … must be calculated as ….
  • A for a and a must be calculated as .

Each pattern is more specific, provides more guidance, and (consequently) less freedom. The last pattern above is even specific to a particular domain.

Sentence patterns seem to be the fashion today. They are not only popular for rules but also used in the descriptions of user stories in agile projects: As a I want so that .

Rules must decrease freedom and so must rule sentence patterns. I am curious about the sentence patterns you use or recognize in your organization. Please send me an e-mail with your examples at silvie@librt.com

Have you changed your mind about rules? Let me know by sharing this post.

This article was originally published by BRCommunity (link).

2017-10-03T11:53:54+00:00Business rules, Rule engine|