Toward safe reuse of product family specifications
Robyn R. Lutz · 1999
Upcoming spacecraft plan extensive reuse of software components, to the extent that some systems will form product families of similar or identical units (e.g., a fleet of spaceborne telescopes).Missions such as these must be demonstrably safe, but the consequences of broad reuse are hard to evaluate from a software safety perspective.This paper reports experience specifying an interferometer (telescope) subsystem as a product family and supplementing the specification with results from a hazards analysis.Lessons learned are discussed in three areas: (1) integration of hazards analysis with the product family approach; (2) modeling decisions that have safety implications (e.g., how to handle near-commonalities, establishing a hierarchy of variabilities, and specifying dependencies among options); and (3) tracing the product family requirements to the design of the reusable components and to the design of a specific product.The product family approach was effective at identifying some latent safety requirements and in validating the design of the reusable software.The product family approach lacked an adequate way to distinguish architectural variations from run-time variations in the model.