Constructing, maintaining, modifying, and adapting operational procedures for manned space operations is a complex task. The procedure author is required to keep track of state constraints such as the location of personnel, equipment, or tools, and of resources such as oxygen, fuel, or power. They must also keep in mind a set of constraints imposing additional restrictions on these procedures. For operations on the International Space Station (ISS), these constraints may be of several different types, including such things as warnings that must be present for a given type of operation, previous actions that must have been taken, tracking the location of personnel, tools, and equipment, or synchronizing operations by different astronauts.
As part of an ongoing research project funded by NASA, Adventium Labs and TRACLabs have designed and implemented an initial version of the Constraint Checking Editor for Procedure Tracking (ConCEPT) system, a constraint checking system for procedures represented in the Procedure Representation Language (PRL). ConCEPT has been integrated into TRACLabs’ Procedure Integrated Development Environment (PrIDE), so that procedures in PRL can be checked against constraints and modified during the process of procedure authoring. The design of ConCEPT, including the types of constraints considered and the integration into the PrIDE user interface, has been validated in discussions with NASA flight controllers.

ISO 14971, the primary medical device risk management standard focuses on single-manufacturer monolithic devices. However, the trend towards medical systems built from reusable platforms and interoperable components produced by different manufacturers introduces a number of additional risk management challenges. In this paper, we revisit the stages of the ISO 14971 risk management process, identify risk management challenges associated with interoperable medical systems that are not sufficiently addressed in ISO 14971, and we discuss possible process, analysis, and management concepts that may be useful in addressing these challenges.

FUSED is a tool integration framework that supports multiple engineers who are collaborating in the development of a diverse set of engineering models used for multiple purposes in multiple phases of development. FUSED is extensible to support a chosen set of modeling environments; a few examples from our work are requirements, solid geometry, computational fluid dynamics, dynamical systems, and vetronics/avionics. An extensible language approach is used, so that many FUSED capabilities are presented to domain experts as minor additions to familiar languages and tools. There is also a special FUSED language to specify compositions of models. Compositions may be used for multiple purposes, e.g., to specify multiple views of a component, verify inter- model consistency, specify part/whole assemblies, or apply design operations to models. One goal of FUSED is to reduce errors due to inconsistencies and emergent properties that occur across multiple models being developed by multiple domain-specific experts. For example, FUSED has an extensible typing and meta-typing system, and compositions may include powerful model verification environments. Another goal is improved support for concurrent, collaborative, mixed- initiative, evolutionary development processes. For example, FUSED was designed to support dependency tracking, change management and ripple effects analyses, version control and remote model server access, and mixed-initiative and multi- disciplinary collaborative optimization.

The structural and electronic properties of the hydrides of silicene and germanene have been studied using ab initio calculations. The trend for the M–H (M= C, Si, and Ge) bond lengths, and corresponding bond energies, is consistent with the atomic size trend, and comparable to those of MH4 hydrides. Band structures were also obtained for the buckled configuration, which is the stable form for both silicene and germanene. Upon hydrogenation, both silicane (indirect gap) and germanane (direct gap) are semiconducting.

In this paper, we describe a tool-set for managing the configuration and management of large-scale networks. In particular, we focus on managing limited processing and communication resources for coordinated network cyber-defense applications. Our implementation encompasses the complete cycle, from initial network modeling and extraction of the relevant constraints, through translation into a formal constraint model, and finally the application of a Linear Programming solver to determine feasibility. This system has been demonstrated on realistic cyber-defense network models provided by domain experts, as well as on automatically-generated models, used to explore the scaling behavior of the system.

We propose a reference architecture aimed at supporting the safety and security of medical devices. The ISOSCELES (Intrinsically Secure, Open, and Safe Cyber-Physically Enabled, Life-Critical Essential Services) architecture is justified by a collection of design principles that leverage recent advances in software component isolation based on hypervisor and other separation technologies. The instantiation of the architecture for particular medical devices is supported by a development process based on Architecture Analysis and Design Language. The architecture models support safety and security analysis as part of a broader risk management framework. The models also can be used to derive skeletons of the device software and to configure the platform’s separation policies and an extensive set of services. We are developing prototypes of the architecture and example medical device instantiations on low-cost boards that can be used in product solutions. The prototype and supporting development and assurance artifacts are being released under an open-source license.

Time series data has been exploited for use with Case Based Reasoning (CBR) in many applications. We present a novel application of CBR that combines intelligent tutoring using Augmented Reality (AR) and prediction. The MonitAR system, presented in this paper, is intended for use as an intelligent guidance system for astronauts conducting complex procedures during periods of a communication time delay or blackout from Earth. Our approach takes advantage of the relational nature of time-series data to detect a task that the user is completing and diagnose the issue when the user is about to make a mistake.

A communications system is provided that includes a communications scheduler adapted to receive messages from a plurality of message sources and sensors. The messages comprise human and generated messages. The sensors comprise situational, neurophysiological and physiological sensors. The cognitive state profile processing unit receives sensor data and produces a current cognitive state profile for the user. The communications scheduler includes a context manager that receives outputs from the plurality of sensors, monitors a current user’s tasks, and retains information about the user’s environment, a message characterization unit that characterizes the messages using the attributes of the message, outputs from the sensors, and the user’s specific baseline profile data and a presentation unit that receives the characterized messages, the cognitive state profile, and context information and queues the characterized messages into a prioritized message list and presents the message list to the user via the display unit.

While creating a software suite of ontology tools for operations, we encountered several reasoner performance scaling issues. This paper describes the symptoms, the diagnosis, and the mitigation strategies used.

This thesis documents several new developments in the theory of parsing, and also the practical value of their implementation in the Copper parser generator.
The most widely-used apparatus for syntactic analysis of programming languages consists of a scanner based on deterministic finite automata, built from a set of regular expressions called the lexical syntax, and a separate parser, operating on the output of this scanner, built from a context-free grammar and utilizing the LALR(1) algorithm.

While the LALR(1) algorithm has the advantage of guaranteeing a non-ambiguous parse, and the approach of keeping the scanner and parser separate make the compilation process more clean and modular, it is also a brittle approach. The class of grammars that can be parsed with an LALR(1) parser is not closed under grammar composition, and small changes to an LALR(1) grammar can remove the grammar from the LALR(1) class. Also, the separation of scanner and parser prevent the use, in any organized way of parser context to resolve ambiguities in the lexical syntax.

One area in which both of these drawbacks pose a particular problem is that of parsing embedded and extensible languages. In particular, it forms one of the last major impediments to the development of an extensible compiler in which language extensions are imported and composed by the end user (programmer) in an analogous manner to the way libraries are presently imported. This is due not only to the problem of the LALR(1) grammar class not being closed under composition, but to the very real possibility that the lexical syntax of two different extensions will clash, making it impossible to construct a scanner without extensive manual resolution of ambiguities, if at all.

This thesis presents three innovations that are a large step towards eliminating parsing as an Achilles’ heel in this application. Firstly, it describes a new algorithm of scanning called context-aware scanning, in which the scanner at each scan is made aware of what sorts of tokens are recognized as valid by the parser at that point. By allowing the use of parser context in the scanner to disambiguate, context-aware scanning makes the specification of embedded languages much simpler — instead of specifying a scanner that must explicitly switch “modes” to scan on the different embedded languages, one simply compiles a context-aware scanner from a single lexical specification, which has implicit “modes” to scan properly on each embedded language. Similarly, in an extensible language, this puts a degree of separation between the lexical syntax of different language extensions, so that any clashes of this sort will not be an issue.

Secondly, the thesis describes an analysis that operates on grammar extensions of a certain form, and can recognize their membership in a class of extensions that can be composed with each other and still produce a deterministic parser—enabling end-users to compose extensions written by different language developers with this guarantee of determinism. The analysis is made practical by context-aware scanning, which ensures a lack of lexical issues to go along with the lack of syntactic nondeterminism. It is this analysis — the first of its kind — that is the largest step toward realizing the sort of extensible compiler described above, as the writer of each extension can test it independently using the analysis and thus resolve any lexical or syntactic issues with the extension before the end user ever sees it.

Thirdly, the thesis describes a corollary of this analysis, which allows extensions that have passed the analysis to be distributed in parse table form and then composed on-the-fly by the end users, with the same guarantee of determinism. Besides expediting the operation of composition, this also enables the use of the analysis in situations where the writer of a language or language extension does not want to release its grammar to the public.

Finally, the thesis discusses how these approaches have been implemented and made practical in Copper, including runtime tests, implementations and analyses of real-world grammars and extensions.