Development Assurance Level
DALSection 06: System Safety & Functional Safety
Definition
A designation of the rigor of the development assurance process applied to a system, software item, or hardware item, based on the severity of the most severe failure condition to which the item contributes. DAL is sometimes referred to as Item Development Assurance Level (IDAL). Five levels are defined: DAL A (most rigorous, associated with catastrophic failure conditions), DAL B (hazardous), DAL C (major), DAL D (minor), and DAL E (no safety effect, no development assurance objectives). The DAL drives the rigor of planning, development, verification, and configuration management activities as specified in standards like DO-178C (software), DO-254 (hardware), and ARP4754B (systems).
Where This Shows Up
DAL is the critical link between safety assessment and development assurance. The safety assessment process (FHA, PSSA) establishes failure condition severity, which determines the DAL for the items that contribute to those failure conditions. The DAL then determines what objectives must be satisfied in the applicable development standards. Higher DALs require more objectives, more independence in verification, and more rigorous processes. DAL assignment is performed as part of the system development process per ARP4754B.
Primary Sources
Defines the concept of development assurance level and the process for assigning DALs to system items.
Uses DAL (referred to as software level) to determine the applicable software development and verification objectives.
Uses DAL to determine hardware design assurance objectives.
Related Terms
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