How to Ensure Requirements Are Clear and Unambiguous

In the field of systems engineering and requirements management, clear and effective communication is crucial. The INCOSE Writing Guide, developed by the International Council on Systems Engineering (INCOSE), serves as a vital tool for creating well-structured and precise requirements.

In conjunction with these guidelines, Innoslate continuously updates its software to align with INCOSE’s standards, ensuring that requirements managed within Innoslate meet industry expectations. The Innoslate Quality Checker is an integral part of this effort, designed to automatically review and enhance the quality of system engineering documentation and models.

In this blog, we will explore how the INCOSE Writing Guide's principles are applied, how the Innoslate Quality Checker supports these standards, and writing tips to ensure your requirements are clear and unambiguous.

What is the INCOSE Writing Guide?

The INCOSE Writing Guide is a resource developed by the International Council on Systems Engineering (INCOSE) to help professionals in the field of systems engineering create clear, consistent, and effective documentation. It provides guidelines and best practices for writing various types of documents, including requirements specifications, design documents, and reports.

The guide focuses on:

• Clarity and Precision: Ensuring that the writing is unambiguous and easily understandable.
• Consistency: Maintaining a uniform style and terminology throughout the document.
• Structure: Organizing content logically to improve readability and usability.
• Best Practices: Incorporating established best practices for documentation in systems engineering.

By following the INCOSE Writing Guide, professionals aim to produce high-quality documents that facilitate stakeholder communication and understanding and support successful system development and integration.

Use the AI Quality Checker for Requirements

The Innoslate Quality Checker is a tool designed to enhance the quality of system engineering documentation and models created within Innoslate. Innoslate is a comprehensive tool for systems engineering and requirements management, and the Quality Checker is one of its features aimed at improving the overall quality of the documents and artifacts produced.

Key functions of the Innoslate Quality Checker include:

• Automated Review: It automatically scans documents and models for common issues such as inconsistencies, missing information, or deviations from established standards.
• Error Detection: Identifies potential errors or problems in the documentation or system models, such as incomplete requirements or logical inconsistencies.
• Compliance Checks: Ensures that the documentation adheres to relevant standards and guidelines, including those specific to systems engineering and industry best practices.
• Improvement Recommendations: Provides suggestions for improving the quality of the documents and models based on predefined criteria or best practices.

The Quality Checker helps streamline the review process, reduce the likelihood of errors, and ensure that documentation is of high quality and suitable for its intended purpose.

Criteria for Clarity

Innoslate’s Quality Checker checks for certain attributes within your requirements. Below is a list of words, phrases, and more to use and avoid in your requirements for ambiguity. Use these criteria to ensure your requirements are unambiguous and pass the quality check.

Units of Measurement

All number values in a requirement should be followed by the unit of measurement from a primary measurement system (i.e., British Imperial, US, Metric). All units of measurement used throughout the requirements document should be consistent with one primary measurement system, whether they are in the abbreviated or regular form.

This follows the INCOSE Rule: R6 - Common Unit of Measure.

Passive Voice

Ensure your requirements do not contain words or phrases using the passive voice. The University of Toronto’s article provides more information and examples of passive voice.

This follows the INCOSE Rule: R2 - Active Voice.

Definite Articles

Indefinite articles such as "a" and "an" should be replaced by the definite article "the."

This follows the INCOSE Rule: R5 - Definite Articles.

Vague Terms

Do not use words/phrases indicating vague terms. Here are some words that provide vague quantification:

Some vague adjectives to avoid are:

Adverbs qualify actions in some way and are particularly troublesome if vague. Avoid vague adverbs, such as “usually,” “approximately,” “sufficiently,” and “typically,” which can lead to ambiguous, unverifiable requirements that do not accurately reflect the stakeholder expectations. Generally, words that end in “-ly” often result in ambiguity.

This follows the INCOSE Rule: R7 - Vague Terms.

Escape Clauses

Do not use words/phrases indicating escape clauses in your requirements. Escape clauses that state vague conditions or possibilities, such as:

This follows the INCOSE Rule: R8 - Avoid Escape Clauses.

Superfluous Infinitives

An infinitive is a verbal consisting of the word “to” + “a verb.” Stay away from phrases indicating unnecessary verbs or passive infinitive phrases such as:

This follows the INCOSE Rule: R10 - Avoid Superfluous Infinitives.

“Not”

Avoid using the word "not” in your requirements. Instead, explicitly state what is required rather than what is not.

This follows the INCOSE Rule: R16 - Use of "Not."

Oblique Symbol

Avoid using the oblique symbol ("/") in your requirements. The symbol is often used to combine synonyms (e.g., symbol/sign), but it can ultimately cause confusion.

This follows the INCOSE Rule: R17 - Use of Oblique Symbol.

Personal and Indefinite Pronouns

Stay away from personal and indefinite pronouns. Some examples of personal pronouns are:

Indefinite pronouns are words such as:

This follows the INCOSE Rule: R24 - Pronouns.

Universal Qualification

Make sure your requirements do not contain words for universal qualifiers such as "all," "any," and "both." These should be replaced by the universal quantifier, "each."

This follows the INCOSE Rule: R32 - Universal Qualification.

Measurable Performance

Avoid words/phrases indicating unmeasurable performance. Unmeasurable words/phrases are ambiguous and need to be replaced by specific quantities within feasible ranges that can be measured. Some words that signal unmeasured quantification are:

This follows the INCOSE Rule: R34 - Measurable Performance.

Temporal Dependencies

Do not use indefinite temporal words/phrases in your requirements such as:

This follows the INCOSE Rule: R35 - Temporal Dependencies.

Acronyms

Make sure to define all acronyms within the project and that each acronym used does not have multiple meanings. For example, do not use AI if your project involves both Artificial Intelligence and Air Interception.

This follows the INCOSE Rule: R37 - Acronyms.

Innoslate’s Acronym Extractor quickly gathers and organizes all document acronyms in a separate reference document.



Tools like the Innoslate Quality Checker can help you comply with the INCOSE Standard and ensure that your requirements are clear and unambiguous.

As you apply the INCOSE Writing Guide and leverage the Innoslate Quality Checker, remember that developing clear, precise, and well-organized requirements is not just a formality but a foundation for effective systems engineering. Ensuring your requirements are well-defined and free from ambiguity will ultimately lead to better project outcomes and system success.