Engineering topics

Goodloe, Alwyn E.

Publications and source records attributed to Goodloe, Alwyn E..

7 records

NASA NTRS2017

Challenges in the Verification of Reinforcement Learning Algorithms

Machine learning (ML) is increasingly being applied to a wide array of domains from search engines to autonomous vehicles. These algorithms, however, are notoriously complex and hard to verify. This work looks at the assumptions underlying machine learning algorithms as well as some of the challenges in trying to verify ML algorithms. Furthermore, we focus on the specific challenges of verifying reinforcement learning algorithms. These are highlighted using a specific example. Ultimately, we do not offer a solution to the complex problem of ML verification, but point out possible approaches for verification and interesting research opportunities.

Van Wesel, Perry↗

NASA NTRS2016

Challenges in High-Assurance Runtime Verification

Safety-critical systems are growing more complex and becoming increasingly autonomous. Runtime Verification (RV) has the potential to provide protections when a system cannot be assured by conventional means, but only if the RV itself can be trusted. In this paper, we proffer a number of challenges to realizing high-assurance RV and illustrate how we have addressed them in our research. We argue that high-assurance RV provides a rich target for automated verification tools in hope of fostering closer collaboration among the communities.

Goodloe, Alwyn E.↗

NASA NTRS2013

Verification of Numerical Programs: From Real Numbers to Floating Point Numbers

Numerical algorithms lie at the heart of many safety-critical aerospace systems. The complexity and hybrid nature of these systems often requires the use of interactive theorem provers to verify that these algorithms are logically correct. Usually, proofs involving numerical computations are conducted in the infinitely precise realm of the field of real numbers. However, numerical computations in these algorithms are often implemented using floating point numbers. The use of a finite representation of real numbers introduces uncertainties as to whether the properties veri ed in the theoretical setting hold in practice. This short paper describes work in progress aimed at addressing these concerns. Given a formally proven algorithm, written in the Program Verification System (PVS), the Frama-C suite of tools is used to identify sufficient conditions and verify that under such conditions the rounding errors arising in a C implementation of the algorithm do not affect its correctness. The technique is illustrated using an algorithm for detecting loss of separation among aircraft.

Goodloe, Alwyn E.↗

NASA NTRS2010

Monitoring Distributed Real-Time Systems: A Survey and Future Directions

Runtime monitors have been proposed as a means to increase the reliability of safety-critical systems. In particular, this report addresses runtime monitors for distributed hard real-time systems. This class of systems has had little attention from the monitoring community. The need for monitors is shown by discussing examples of avionic systems failure. We survey related work in the field of runtime monitoring. Several potential monitoring architectures for distributed real-time systems are presented along with a discussion of how they might be used to monitor properties of interest.

Goodloe, Alwyn E.↗

NASA NTRS2009

Compositional Verification of a Communication Protocol for a Remotely Operated Vehicle

This paper presents the specification and verification in the Prototype Verification System (PVS) of a protocol intended to facilitate communication in an experimental remotely operated vehicle used by NASA researchers. The protocol is defined as a stack-layered com- position of simpler protocols. It can be seen as the vertical composition of protocol layers, where each layer performs input and output message processing, and the horizontal composition of different processes concurrently inhabiting the same layer, where each process satisfies a distinct requirement. It is formally proven that the protocol components satisfy certain delivery guarantees. Compositional techniques are used to prove these guarantees also hold in the composed system. Although the protocol itself is not novel, the methodology employed in its verification extends existing techniques by automating the tedious and usually cumbersome part of the proof, thereby making the iterative design process of protocols feasible.

Goodloe, Alwyn E.↗

NASA NTRS2009

From Verified Models to Verifiable Code

Declarative specifications of digital systems often contain parts that can be automatically translated into executable code. Automated code generation may reduce or eliminate the kinds of errors typically introduced through manual code writing. For this approach to be effective, the generated code should be reasonably efficient and, more importantly, verifiable. This paper presents a prototype code generator for the Prototype Verification System (PVS) that translates a subset of PVS functional specifications into an intermediate language and subsequently to multiple target programming languages. Several case studies are presented to illustrate the tool's functionality. The generated code can be analyzed by software verification tools such as verification condition generators, static analyzers, and software model-checkers to increase the confidence that the generated code is correct.

Lensink, Leonard↗

NASA NTRS2009

Design and Verification of a Distributed Communication Protocol

The safety of remotely operated vehicles depends on the correctness of the distributed protocol that facilitates the communication between the vehicle and the operator. A failure in this communication can result in catastrophic loss of the vehicle. To complicate matters, the communication system may be required to satisfy several, possibly conflicting, requirements. The design of protocols is typically an informal process based on successive iterations of a prototype implementation. Yet distributed protocols are notoriously difficult to get correct using such informal techniques. We present a formal specification of the design of a distributed protocol intended for use in a remotely operated vehicle, which is built from the composition of several simpler protocols. We demonstrate proof strategies that allow us to prove properties of each component protocol individually while ensuring that the property is preserved in the composition forming the entire system. Given that designs are likely to evolve as additional requirements emerge, we show how we have automated most of the repetitive proof steps to enable verification of rapidly changing designs.

Munoz, Cesar A.↗