Duncan Clarke

Assessing Mental Workload During Laparoscopic Surgery

Although the use of performance efficiency measures (speed, movement economy, errors) and ergonomic assessments are relatively well established, the evaluation of cognitive outcomes is rare. This report makes the case for assessment strategies that include mental workload measures as a way to improve training scenarios and training/operating environments. These mental workload measures can be crucially important in determining the difference between well-intentioned but subtly distracting technologies and true breakthroughs that will enhance performance and reduce stress.

Automatic generation of tests for timing constraints from requirements

The authors present a framework for testing timing constraints of real-time systems. The tests are automatically derived from specifications of minimum and maximum allowable delays between input/output events in the execution of a system. The test derivation scheme uses a graphical specification formalism for timing constraints, and the real-time process algebra Algebra of Communicating Shared Resources (ACSR) for representing tests and process models. The use of ACSR to describe test sequences has two main advantages. First, tests can be applied to an ACSR model of the software system within the ACSR semantic framework for model validation purposes. Second, ACSR has concise notation and a precise semantics that will facilitate the translation of real-time tests into a software test language for software validation purposes.

Schedulability analysis of AADL models

The paper discusses the use of formal methods for the analysis of architectural models expressed in the modeling language AADL. AADL describes the system as a collection of interacting components. The AADL standard prescribes semantics for the thread components and rules of interaction between threads and other components in the system. We present a semantics-preserving translation of AADL models into the real-time process algebra ACSR, allowing us to perform schedulability analysis of AADL models

A Process Algebraic Approach to the Schedulability Analysisof Real-Time Systems

To engineer reliable real-time systems, it is desirable to detect timing anomalies early in the development process. However, there is little work addressing the problem of accurately predicting timing properties of real-time systems before implementations are developed. This paper describes an approach to the specification and schedulability analysis of real-time systems based on the timed process algebra ACSR-VP, which is an extension of ACSR with value-passing communication and dynamic priorities. Combined with the existing features of ACSR for representing time, synchronization and resource requirements, ACSR-VP is capable of specifying a variety of real-time systems with different scheduling disciplines in a modular fashion. Moreover, we can use VERSA, a toolkit we have developed for ACSR, to perform schedulability analysis on real-time systems specified in ACSR-VP automatically by checking for a certain bisimulation relation.

Automatic test generation for the analysis of a real-time system: Case study

We present a framework for testing timing constraints of real-time systems. Our tests are automatically derived from specifications of minimum and maximum allowable delays between input/output events in the execution of a system. Our test derivation scheme uses a graphical specification formalism for timing constraints, and the real-time process algebra Algebra of Communicating Shared Resources (ACSR) for representing tests and process models. The use of ACSR to describe test sequences has two main advantages. First, tests can be applied to an ACSR model of the software system within the ACSR semantic framework for model validation purposes. Second, ACSR has concise notation and a precise semantics that will facilitate the translation of real-time tests into a software test language for software validation purposes. The major benefit of our approach is that it can be used to validate a design specification which has too many states for exhaustive state space exploration based analysis. As an illustration of this benefit, we describe the case study of using the automatic derivation of tests from timing specifications for the analysis of the Philips Audio Control Protocol.

Testing real-time constraints in a process algebraic setting

Verifying timing properties of real-time systems by traditional approaches that depend on the exploration of the entire system state space is impractical for large systems. In contrast, testing allows the search for violations of a property to be narrowed to a relatively small portion of the overall state space, based on assumptions regarding the structure of an implementation. We present a domain testing based technique for verifying timing constraints of real-time systems, given timing constraints specified as minimum and maximum allowable delays between input/output events. The testing methodology is presented in a process algebraic setting where it is an efficient alternative to model checking for verifying system timing properties. An example illustrates the application of our testing technique to a timed interactive system.

Process-Algebraic Interpretation of AADL Models

We present a toolset for the behavioral verification and validation of architectural models of embedded systems expressed in the language AADL. The toolset provides simulation and timing analysis of AADL models. Underlying both tools is a process-algebraic implementation of AADL semantics. The common implementation of the semantics ensures consistency in the analysis results between the tools.

A new technique for the digitization and restoration of deteriorated photographic negatives

This work describes the development and analysis of a new image-based photonegative restoration system. Deteriorated acetate-based safety negatives are complex objects due to the separation and channeling of their multiple layers that has often occurred over 70 years time. Using single-scatter diffuse transmission model, the intrinsic intensity information and shape distortion of film can be modeled. A combination of structured-light and high-dynamic range imaging is used to acquire the data which allows for automatic photometric and geometric correction of the negatives. This is done with a simple-to-deploy and cost-effective camera and LCD system that are already available to most libraries and museums. An initial analysis is provided to show the accuracy of this method and promising results of restoration of actual negatives from a special archive collection are then produced.

Stereo endoscopy as a 3-D measurement tool

Stereoscopic endoscopes restore much of the sense of depth perception lost in minimally invasive surgery techniques. They also open the possibility of anatomical reconstruction from in-vivo video using established computer vision techniques. However, limitations in computational power, as well as imaging constraints due to specularities, color, and movement, make full three-dimensional reconstruction difficult to achieve in real time. We demonstrate that a subset of this reconstruction problem, the ability to take accurate anatomical measurements, can be trivially achieved using current stereo-endoscopes and well-known algorithms. After careful calibration of the camera pair, we track the surgical instruments, which present the strongest features in the operating scene. The three-dimensional positions of the tips of the instruments are automatically calculated in real-time, and the computation of the distance between them allows for accurate measurements of any anatomical region within reach of the instrument tips.

PARAGON: a paradigm for the specification, verification and testing of real-time systems

The PARAGON toolset provides an environment for the modular and hierarchical design of resource-bound, real-time systems. It offers well-integrated graphical and textual specification languages with formal semantics. Both languages are based on the Algebra of Communicating Shared Resources (ACSR), a process algebra with explicit notions of time, resources and priority. The integration of the three notions widens the applicability of the PARAGON formalisms to embedded systems, control systems, and fault-tolerant systems where run-time resource requirements must be considered during the design phase. To facilitate the design of complex systems, PARAGON allows a designer to describe a system incrementally through refinement steps that preserve system properties. To increase dependability of system models, PARAGON offers three types of analysis: automated verification of system requirements, interactive simulation, and testing. In this paper, we demonstrate the design methodology that PARAGON offers through examples.