This paper describes ongoing work on a new technique for reducing the cost of assurance of large software systems by building on a verified component platform. From a component architecture description, we automatically derive a formal model of the system and a semantics for the runtime behaviour of generated inter-component communication code. We can prove wellformedness properties of the architecture automatically and provide a framework in which users can reason about their component code and its behaviour. By leveraging the isolation properties and communication guarantees of a formally verified platform, correctness arguments for critical components will be able to be derived independently and composed together to reason about system-level correctness.

Device drivers are notorious for being a major source of failure in operating systems. In analysing a sample of real defects in Linux drivers, we found that a large proportion (39%) of bugs are due to two key shortcomings in the device-driver architecture enforced by current operating systems: poorly-defined communication protocols between drivers and the OS, which confuse developers and lead to protocol violations, and a multithreaded model of computation that leads to numerous race conditions and deadlocks.

Faulty device drivers cause significant damage through down time and data loss. The problem can be mitigated by an improved driver development process that guarantees correctness by construction. We achieve this by synthesising drivers automatically from formal specifications of device interfaces, thus reducing the impact of human error on driver reliability and potentially cutting down on development costs.

The lack of well-defined protocols for interaction with the operating system is a common source of defects in device drivers. In this paper we investigate the use of a formal language to define these protocols unambiguously. We present a language that allows us to convey all important requirements for driver behaviour in a compact specification and that can be readily understood by software engineers. It is intended to close the communication gap between OS and driver developers and enable more reliable device drivers.

Despite the extensive use of caching techniques, the Web is overloaded. While the caching techniques currently used help some, it would be better to use different caching and replication strategies for different Web pages, depending on their characteristics. We propose a framework in which such strategies can be devised independently per Web document. A Web document is constructed as a worldwide, scalable distributed Web object. Depending on the coherence requirements for that document, the most appropriate caching or replication strategy can subsequently be implemented and encapsulated by the Web object. Coherence requirements are formulated from two different perspectives: that of the Web object, and that of clients using the Web object. We have developed a prototype in Java to demonstrate the feasibility of implementing different strategies for different Web objects.