Business Rules – May 2009

What is a Sentence Form?
Definition and Purpose

A Sentence Form is a basic pattern or template in natural language that can be used to express a certain kind of business rule in a consistent, well-organized
manner. Each Sentence Form is aimed for a particular kind of guidance.

The purpose of the RuleSpeakR Sentence Forms is to ensure that written business rules are more easily understood. They also help ensure that
different practitioners working on a large set of business rules express the same ideas in the same way. Such consistency would not be possible if business rules were expressed in a completely
“free-form” manner. 

The Sentence Forms are not technical in nature. In other words, they do not represent a formal language or syntax for implementing business rules using a software platform (e.g., a rule engine).
Rather, they are aimed at expressing business rules to improve communication at the business level.




Success Factors for the Sentence Forms
What is important – and what is not important – when applying the RuleSpeak Sentence Forms? One thing
that should not be considered is how the business rules will actually be implemented using a particular rule engine or programming language. What matters above all else is effective business
communication. Sticking to that perspective sometimes proves difficult for those responsible for technical implementation. They may want to get to the IT versions directly. But doing that will not
help with capturing the business rules succinctly from the business perspective.

Using the Sentence Forms to express business rules does require a modest measure of discipline. This discipline can be achieved through a bit of practice and by understanding certain fundamentals.
These fundamentals are discussed later in this document.

Finally, it is important to understand the level of business rules to which the Sentence Forms should be applied. As above, the Sentence Forms are not aimed at system design or automation. They are
also not aimed at the highest forms of guidance – that is, the language of laws, regulations, contracts, business policies, etc.

Rather, the Sentence Forms are aimed at what is called practicable guidance. Practicable business rules are ones used to make operational business decisions on
a day-in-and-day-out basis. If a business worker is properly authorized, and understands the business vocabulary, he or she should be able to apply the practicable business rules directly in the
conduct of ongoing business activity.

Often, these practicable business rules must be interpreted from the higher forms of guidance in order to clarify, disambiguate and solidify their business intent. The Sentence Forms facilitate such
interpretation by providing predictable patterns of expression. The same is true if practicable business rules are being reverse-engineered bottom-up from existing implementations or documentation,
or harvested on a facilitated basis from subject-matter experts.




Usage Notes

• “Shall” – Highest forms of guidance – laws, regulations, contracts, business policies, etc. – often use the word “shall.” We prefer the less formal
  word “must,” which is generally more appropriate for practicable business rules.

• “Should” – Any business rule can be stated using “should” instead of “must.” Using “should,” however, reflects an assumption or decision
  about the appropriate enforcement level of a business rule. We prefer to document any sense of how strictly a business rule is to be enforced separately from
  the expression of the business rule itself. We therefore prefer always using the word “must” instead of “should.”

• “May” – We always use the word “may” in the sense of something being allowed (or disallowed). We never use “may” in the sense of “might”
  – i.e., that something might occur or might be true. Unfortunately, “may” does have this double usage
  in English, but no suitable alternative exists. In any event, experience has proven that the correct sense “is allowed” quickly wins out.

Basic Concepts
Understanding fundamental ideas about expressing business rules will assist greatly in writing them effectively. Briefly, these ideas are as follows.

Every business rule statement should use a rule keyword: Every business rule can be expressed using one of the following two words.

• “must”
• “only”

These fundamental words are called the RuleSpeak Rule Keywords. It is very important that every business rule statement include exactly one of these two
rule keywords.

Practicable guidance comes in two varieties: A business rule always removes a degree of freedom. The presence of one of the two rule keywords in a sentence
clearly indicates that intent.

A large majority of sentences typically expressed to give guidance are business rule statements. Sometimes, however, practicable guidance is worth expressing that does not remove a degree of freedom.
Such a statement, which simply clarifies that something is allowed, or that something is not required, is called a
statement of advice.

A statement of advice should never include either of the two rule keywords. Instead, it should use exactly one of the following two RuleSpeak Advice
Keywords.

• “may”
• “need not”

Note that “may” coupled with “only” in the same sentence always produces a business rule, not an advice. Statements of advice and business rule statements are both
guidance statements.

Every guidance statement should be a complete sentence: English helps ensure wonderful completeness in the communication of thoughts (propositions) through
grammatical rules about forming sentences. Follow those rules religiously in writing all guidance statements.

Every guidance statement should have a subject: In good English construction, every sentence has a subject. Although this subject may be implied or the sentence inverted, more often than not an
explicit subject appears as the first word or phrase in the main body of the sentence. Such sentences are usually direct, and if well written, easy to follow. (The subject in the previous sentence,
for example, is “sentences.”)

RuleSpeak prescribes that guidance statements have an explicit subject at the beginning. This subject should be a noun, possibly qualified. The singular form is
preferred. This approach promotes overall clarity and consistency.

Many IT notations feature “If … then…” syntax for implementing business rules in rule engines or programming languages. In such notations, the true subject does not appear
until after the “if” clause.

Besides being “unfriendly” for business communication, such syntax is problematic for expressing certain types of guidance. What, for example, is the “if” of the business rule
statement, “An employee must have a name.”?

Any guidance statement may reference an instance: An instance is a single thing, rather than a class of things. Instances can be referenced by guidance
statements just as can classes of things. If there could be any doubt as to whether a term in a guidance statement refers to an instance or a class, the prudent approach is to put the term in single
quotes.

Qualifying guidance statements: Most guidance statements include some qualification(s) indicating the circumstances under which they apply. Often – but by
no means always – such qualification is expressed using “if.”

Guidance that applies only at some point(s) in time: The word “if” indicates that qualification is continuous over time. The word “when”
should be used if a guidance statement applies only at certain point(s) in time.

As stated, this business rule applies only at each point in time when a student registers for some semester. At any other time, the business rule is assumed not to apply; that is, the total
enrollment fee amount owed for the semester does not have to be $5,065 (and probably increases!).

Allowing something conditionally: The Sentence Form “… may … if …” (without an “only”) should always be avoided. Statements using that Sentence Form are quite tricky and can be easily misunderstood.

This statement expresses an advice. (This interpretation is dictated by logic.) It covers only the situation in which some proof of purchase is provided. It literally does not say anything about whether an item may be returned if some proof of purchase is not provided. Most likely, however, the business
intent was to disallow returns without providing some proof of purchase. Assuming that to be the case, the Rule Keyword “only” should be inserted as follows, thereby turning the advice
into a business rule.

How to say something is not a business rule under certain circumstances: If something is not a business rule under certain circumstances, the best Sentence Form
to express the advice is generally “ … need not … if …”.

Note that by itself, this statement of advice leaves open the question of whether credit checks are required for orders that total $1,000 or more. If such credit checks are required, a separate
business rule statement must be expressed. The general point to remember about expressing guidance is that nothing is ever required (that is, everything is allowed) unless a business rule explicitly
removes some degree of freedom.

End Note:

1. RuleSpeak was one of three reference notations used in the creation of SBVR (Semantics of Business Vocabulary and Business Rules) and is consistent with
   that standard. RuleSpeak is a technique of ProteusR – the BRS methodology for business analysis and business rules. RuleSpeakR
   is a registered trademark of Business Rule Solutions, LLC. Read more about RuleSpeak on www.RuleSpeak.com.