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3-Step Guide to Defining Requirements for DO-178C

3-Step Guide to Defining Requirements for DO-178C

Table of Contents

Introduction

Defining requirements is a critical aspect of developing software for safety-critical systems. In the aviation industry, compliance with the DO-178C standard is crucial for ensuring the safety and reliability of airborne software. DO-178C provides guidance for the certification of software used in airborne systems, and one of its key aspects is the proper definition of requirements. This article presents a comprehensive 3-step guide to help software engineers and development teams define requirements in accordance with DO-178C.

Step 1: Establish a Requirements Framework

Identify the Stakeholders

The first step in defining requirements for DO-178C is to identify the stakeholders involved in the software development process. Stakeholders can include system engineers, software engineers, verification engineers, safety assessors, and regulatory authorities. By identifying and involving the right stakeholders from the beginning, you ensure that all perspectives are considered, and potential conflicts or misunderstandings are addressed early on.

Define System-Level Requirements

After identifying the stakeholders, it is crucial to define system-level requirements. These requirements describe the overall behavior and functionality of the software within the context of the airborne system. System-level requirements should be concise, clear, and unambiguous to avoid any misinterpretation during the development and certification process.

To define system-level requirements effectively, consider the following:

  • Understand the intended purpose of the software and its interactions with other system components.
  • Identify the safety-critical aspects that need to be addressed.
  • Specify the functional and performance requirements.
  • Define the environmental and operational constraints.
  • Establish the interfaces and data flows between the software and other system components.

Create High-Level Software Requirements

Once the system-level requirements are established, the next step is to create high-level software requirements. These requirements elaborate on the system-level requirements and provide more detailed information about the software functionality. High-level software requirements should be traceable to the system-level requirements and provide a clear roadmap for the software development process.

Consider the following points when creating high-level software requirements:

  • Decompose the system-level requirements into smaller, manageable units.
  • Specify the input and output data formats, data integrity requirements, and data transfer mechanisms.
  • Define the software interfaces, including external interfaces and internal module interfaces.
  • Identify the data processing algorithms and their expected behavior.
  • Document any timing or performance constraints imposed on the software.

Step 2: Ensure Requirement Consistency and Completeness

Perform Requirements Review

Once the high-level software requirements are created, it is essential to conduct a comprehensive requirements review. The review process involves evaluating the requirements for consistency, completeness, and correctness. Reviewing requirements with all relevant stakeholders helps identify any missing or contradictory requirements and ensures that the requirements accurately reflect the intended software behavior.

During the review process, pay attention to the following:

  • Verify that each high-level software requirement can be traced back to a corresponding system-level requirement.
  • Check for any missing requirements or ambiguous statements.
  • Ensure that the requirements are free from contradictions or conflicts.
  • Validate that the requirements are realistic and achievable within the given constraints.
  • Involve verification engineers and safety assessors to assess the verifiability and safety implications of the requirements.

Establish a Requirements Traceability Matrix

To maintain a clear link between system-level and high-level software requirements, it is essential to establish a requirements traceability matrix (RTM). An RTM provides a structured way to track the relationships between requirements, ensuring that every requirement is accounted for and verified during the software development process.

When creating an RTM, consider the following steps:

  • List all system-level requirements in one column.
  • Create corresponding columns for high-level software requirements, verification activities, and test cases.
  • Establish traceability links between system-level and high-level software requirements.
  • Update the RTM throughout the software development lifecycle to reflect changes and additions to the requirements.
  • Use the RTM as a tool for verification planning, ensuring that all requirements are tested and verified.

Step 3: Document and Maintain Requirements

Document Requirements

Once the requirements have been defined, reviewed, and traced, it is crucial to document them thoroughly. Proper documentation ensures that the requirements are accessible to all stakeholders and serves as a reference throughout the software development and certification process.

When documenting requirements, consider the following guidelines:

  • Use a consistent format and structure for all requirements.
  • Clearly state the requirement, including any necessary inputs, expected outputs, and constraints.
  • Include rationale and reasoning behind each requirement to provide context.
  • Assign unique identifiers to each requirement for easy reference and traceability.
  • Update the documentation whenever a requirement is modified, added, or removed.

Maintain Requirements

Requirements are not static; they may evolve and change throughout the software development lifecycle. It is crucial to establish a robust change management process to handle requirement updates and ensure that all changes are properly documented and approved.

When maintaining requirements, consider the following:

  • Establish a designated change control board responsible for reviewing and approving requirement changes.
  • Clearly define the process for requesting, reviewing, and implementing requirement changes.
  • Update the requirements documentation and the RTM whenever a change is approved.
  • Communicate requirement changes to all relevant stakeholders to ensure everyone is working with the most up-to-date information.

Using Visure Solutions for Defining Requirements for DO-178C

Introduction

Defining requirements for software development in compliance with DO-178C can be a complex and challenging task. To streamline this process and ensure adherence to the standard, organizations can leverage advanced requirements management tools. Visure Solutions offers a comprehensive software solution that facilitates the definition, management, and traceability of requirements for DO-178C projects. This article explores how Visure Solutions can be used effectively to define requirements in accordance with DO-178C guidelines.

Visure Solutions: An Overview

Visure Solutions is a leading provider of requirements management software, offering a dedicated tool called “Visure Requirements” that supports the development of safety-critical systems, including those governed by DO-178C. The Visure Requirements tool provides a collaborative and integrated platform for capturing, organizing, and tracking requirements throughout the software development lifecycle.

Key Features and Benefits

Requirements Elicitation and Capture

Visure Requirements offers a user-friendly interface for capturing and eliciting requirements. Users can create, import, or link requirements from various sources, such as documents, spreadsheets, or existing databases. The tool allows for structured and organized requirement management, ensuring that all relevant information is captured and easily accessible.

Requirements Traceability

Ensuring traceability between requirements is essential for DO-178C compliance. Visure Solutions provides a powerful traceability feature that allows users to establish and maintain trace links between system-level requirements, high-level software requirements, verification activities, and test cases. This feature enables comprehensive impact analysis, change management, and verification planning, ensuring that all requirements are properly addressed and validated.

Version Control and Baseline Management

Visure Requirements incorporates version control and baseline management capabilities, enabling users to track changes and manage different versions of requirements. This functionality is crucial for maintaining a clear audit trail and ensuring that requirements are properly controlled throughout the software development process. It allows for easy identification and retrieval of previous versions and supports configuration management practices.

Collaboration and Review

The Visure Requirements tool facilitates collaboration among stakeholders involved in the requirements definition process. It provides features for real-time collaboration, comments, and notifications, allowing teams to work together efficiently. Additionally, the tool supports comprehensive review workflows, enabling stakeholders to review and approve requirements, ensuring consistency and completeness.

Compliance and Documentation

Visure Requirements helps organizations comply with DO-178C by providing customizable templates and predefined attributes aligned with the standard’s guidelines. The tool allows users to generate requirement documents automatically, ensuring consistency and saving time in the documentation process. It also supports the generation of reports and traceability matrices, which are essential artifacts for regulatory compliance and certification audits.

Using Visure Solutions for DO-178C Compliance

To effectively use Visure Solutions for defining requirements in compliance with DO-178C, follow these steps:

Set Up the Project

Create a new project in Visure Requirements specifically tailored for your DO-178C software development. Define project-specific settings, such as naming conventions, access control, and predefined attributes aligned with DO-178C guidelines.

Define System-Level Requirements

Start by capturing system-level requirements using the requirements elicitation and capture features of Visure Requirements. Clearly define the intended purpose of the software, its interactions with other system components, safety-critical aspects, functional and performance requirements, environmental and operational constraints, and interfaces with other system elements.

Create High-Level Software Requirements

Using the traceability feature, link the system-level requirements to high-level software requirements. Decompose the system-level requirements into smaller, manageable units and provide more detailed information about the software functionality. Specify input/output formats, data integrity requirements, software interfaces, data processing algorithms, timing constraints, and performance requirements.

Establish Traceability and Perform Reviews

Leverage the traceability capabilities of Visure Requirements to establish trace links between system-level requirements, high-level software requirements, verification activities, and test cases. Conduct comprehensive reviews to ensure requirement consistency, completeness, and correctness. Use the collaboration and review features to engage stakeholders and gather feedback effectively.

Document and Generate Reports

Document the defined requirements using the customizable templates provided by Visure Requirements. Take advantage of the version control and baseline management features to track changes and maintain proper documentation control. Generate requirement documents, traceability matrices, and other necessary reports to support compliance and certification activities.

Conclusion

Defining requirements in accordance with DO-178C is a crucial step in developing software for safety-critical systems in the aviation industry. By following the 3-step guide presented in this article, development teams can establish a solid foundation for creating reliable and compliant software. Remember to establish a requirements framework, ensure requirement consistency and completeness, and document and maintain requirements throughout the software development lifecycle. By adopting these best practices, organizations can enhance the quality and safety of their airborne software while meeting the stringent requirements of DO-178C.

Visure Solutions’ Visure Requirements tool offers a robust platform for effectively defining, managing, and tracing requirements for DO-178C compliance. By leveraging the features and capabilities of Visure Requirements, organizations can streamline the requirements definition process, enhance collaboration among stakeholders, ensure traceability, and generate necessary documentation for regulatory compliance. Incorporating Visure Solutions into the software development lifecycle can significantly contribute to the successful development and certification of software in accordance with DO-178C guidelines. Experience the power of our comprehensive platform with a free 30-day trial, and witness firsthand how it can effectively support your software development and verification requirements in full compliance with the DO-178B/C standard.

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