Trusted product lines

This thesis describes research undertaken into the application of software product line approaches to the development of high-integrity, embedded real-time software systems that are subject to regulatory approval/certification. The motivation for the research arose from a real business need to reduce cost and lead time of aerospace software development projects.

The thesis hypothesis can be summarised as follows:

It is feasible to construct product line models that allow the specification of required behaviour within a reference architecture that can be transformed into an effective product implementation, whilst enabling suitable supporting evidence for certification to be produced.

The research concentrates on the following four main areas:

1. Construction of an argument framework in which the application of product line techniques to high-integrity software development can be assessed and critically reviewed.

2. Definition of a product-line reference architecture that can host components containing variation.

3. Design of model transformations that can automatically instantiate products from a set of components hosted within the reference architecture.

4. Identification of verification approaches that may provide evidence that the transformations designed in step 3 above preserve properties of interest from the product line model into the product instantiations.

Together, these areas form the basis of an approach we term “Trusted Product Lines”. The approach has been evaluated and validated by deployment on a real aerospace project; the approach has been used to produce DO-178B/ED-12B Level A applications of over 300 KSLOC in size. The effect of this approach on the software development process has been critically evaluated in this thesis, both quantitatively (in terms of cost and relative size of process phases) and qualitatively (in terms of software quality).

The “Trusted Product Lines” approach, as described within the thesis, shows how product line approaches can be applied to high-integrity software development, and how certification evidence created and arguments constructed for products instantiated from the product line. To the best of our knowledge, the development and effective application of product line techniques in a certification environment is novel and unique.