Code generation for a family of executable modelling notations

We are investigating semantically configurable model-driven engineering (MDE). The goal of this work is a modelling environment that supports flexible, configurable modelling notations, in which specifiers can configure the semantics of notations to suit their needs and yet still have access to the types of analysis tools and code generators normally associated with MDE. In this paper, we describe semantically configurable code generation for a family of behavioural modelling notations. The family includes variants of statecharts, process algebras, Petri Nets, and SDL88. The semantics of this family is defined using template semantics, which is a parameterized structured operational semantics in which parameters represent semantic variation points. A specific notation is derived by instantiating the family’s template semantics with parameter values that specify semantic choices. We have developed a code-generator generator (CGG) that creates a suitable Java code generator for a subset of derivable modelling notations. Our prototype CGG supports 26 semantics parameters, 89 parameter values, and 7 composition operators. As a result, we are able to produce code generators for a sizable family of modelling notations, though at present the performance of our generated code is about an order of magnitude slower than that produced by commercial-grade generators.     

Deconstructing the semantics of big-step modelling languages

With the popularity of model-driven methodologies and the abundance of modelling languages, a major question for a requirements engineer is: which language is suitable for modelling a system under study? We address this question from a semantic point-of-view for big-step modelling languages (BSMLs). BSMLs are a class of popular behavioural modelling languages in which a model can respond to an input by executing multiple transitions, possibly concurrently. We deconstruct the operational semantics of a large class of BSMLs into eight high-level, mostly orthogonal semantic aspects and their common semantic options. We analyse the characteristics of each semantic option. We use feature diagrams to present the design space of BSML semantics that arises from our deconstruction, as well as to taxonomize the syntactic features of BSMLs that exhibit semantic variations. We enumerate the dependencies between syntactic and semantic features. We also discuss the effects of certain combinations of semantic options when used together in a BSML semantics. Our goal is to empower a requirements engineer to compare and choose an appropriate BSML from the plethora of existing BSMLs, or to articulate the semantic features of a new desired BSML when such a BSML does not exist.     

Module reuse by interface adaptation

This paper describes a language called Nimble that allows designers to declare how the actual parameters in a procedure call are to be transformed at run time. Normally, programmers must edit an application's source in order to adapt it for reuse in some new context where the interfaces fail to match exactly (e.g. the parameters may appear in a different order, data types may not exactly match, and some data may need to be either initialized or masked out when the reusable module is integrated within a new application.) But Nimble allows programmers to adapt the interfaces of existing software without having to operate on the source manually. As a result, existing software may be easily reused in a broader range of applications, and software libraries do not need to store many variants of a component that differ only in how the interfaces are used. Nimble has been implemented on a variety of Unix hosts, and is part of a broader reuse project at the University of Maryland. Our current system is suitable for use either in conjunction with existing module interconnection languages, or stand-alone with C, Pascal and Ada source programs.     

Operational sustainability metrics assessing metric effectiveness in the context of electronics-recycling systems

In the past 15 years corporations and governments have developed a growing appreciation of the need for sustainability. However, there is still little clarity on how to move toward the goal of sustainability or measure improvements. Not only are there currently few operational metrics by which to practically assess progress toward sustainability, there is also little understanding of how to judge the effectiveness of such metrics. This paper presents a pragmatic approach to developing--and evaluating--system-specific performance metrics for sustainability. Electronics recycling is used as a case problem in developing and judging the effectiveness of such metrics. Despite growing concerns aboutthe handling of end-of-life electronics, data availability is inconsistent, and there is still limited understanding of the electronics-recycling system as a whole. To begin to address the need for practical quantitative methods to assess system performance, several indicators were developed and applied to three U.S. electronics-recycling operations. These metrics were assessed based on the developed criteria that effective measures be useful, robust, and feasible. Results show that the current measure of "mass percent to landfill" is not sufficient to assess system performance. Relevance-weighted mass indicators with varying data requirements can provide additional insights on resource efficiency.     

RE 05: Engineering Successful Products

At the Requirements Engineering conference series, researchers and practitioners exchange experiences, discuss problems, and propose solutions. The theme of RE 05--Engineering Successful Products--reflects the understanding that high-quality requirements are at the heart of successful products. To be successful, developers must understand the goals and needs of users, customers, and other stakeholders and must build products that address these goals.     

State-based model checking of event-driven system requirements

It is demonstrated how model checking can be used to verify safety properties for event-driven systems. SCR tabular requirements describe required system behavior in a format that is intuitive, easy to read, and scalable to large systems (e.g. the software requirements for the A-7 military aircraft). Model checking of temporal logics has been established as a sound technique for verifying properties of hardware systems. An automated technique for formalizing the semiformal SCR requirements and for transforming the resultant formal specification onto a finite structure that a model checker can analyze has been developed. This technique was effective in uncovering violations of system invariants in both an automobile cruise control system and a water-level monitoring system     

Anesthetics and automaticity of dominant and latent pacemakers in chronically instrumented dogs. I. Methodology, conscious state, and halothane anesthesia: comparison with and without muscarinic blockade during exposure to epinephrine

BACKGROUND: Supraventricular dysrhythmias are common during anesthesia, but have been incompletely investigated. Mechanisms may involve altered automaticity of subsidiary pacemakers and participation of vagal reflexes. The following hypotheses were tested: (1) shifts from the sinoatrial (SA) node to subsidiary pacemakers require intact vagal reflexes and (2) halothane sensitizes the heart to epinephrine-induced atrial pacemaker shifts. METHODS: Epicardial electrodes were implanted in eight dogs on both atrial appendages, the right ventricle, along the sulcus terminalis, and at the His bundle. Weekly testing awake (control), awake with atropine methylnitrate, with 1 and 2 micrograms epinephrine.kg-1.min-1 (3 min-infusions), and under 1.25 and 2 MAC halothane was performed. Electrograms were analyzed for the site of earliest activation (SEA), which was scored 1-6 depending on the distance from the SA node, and expressed as the SEA value. RESULTS: In conscious dogs (control) and at 1.25 MAC halothane, epinephrine increased the SEA values (shifted activation from SA node) and blood pressure, and decreased heart rate; however, with atropine, SEA values were unaffected by epinephrine, although blood pressure and heart rate were elevated. At 2 MAC, atropine did not affect the epinephrine-induced increase in SEA values. Halothane increased SEA values when combined with 1 micrograms epinephrine.kg-1.min-1. CONCLUSIONS: Pacemaker shifts account for atrial dysrhythmias in the conscious state and during 1.25 MAC halothane with epinephrine, and require vagal participation. Halothane sensitizes the heart to epinephrine-induced atrial dysrhythmias. Atropine and halothane facilitate His bundle beats during exposure to epinephrine.     

A Microcomputer-Based Neuromuscular Blockade Monitor

A portable device has been developed and tested for monitoring the effects of neuromuscular blocking drugs. It incorporates a nerve stimulator, force transducer, and microcomputer for quantitating the level of neuromuscular block. The nerve stimulator, under microcomputer control, is capable of delivering single shocks at 0.1 Hz, train-of-four stimulation at 2 Hz, and tetanic stimulation at 30, 100, or 200 Hz. Stimuli are applied to the ulnar nerve. The response, adduction of the thumb, is sensed by a flexible beam force transducer. The output of the transducer is amplified and then processed by the microcomputer. The microcomputer quantitates twitch and train-of-four responses, and calculates the ratio between the first and fourth responses of train-of-four. The ratio is used to estimate the level of block. The device has clinical potential as a trend monitor of neuromuscular function during anesthesia and surgery. It also has research potential for determining the effects of newer neuromuscular blocking drugs for comparison with presently used drugs or, alternatively, for determining the effects of blocking drugs in altered physiological states.     

Precision and accuracy of two luminescence dating techniques for retrospective dosimetry: SAR-OSL and SAR-ITL

Luminescence techniques based on thermally or optically stimulated signals are used extensively for estimating the equivalent dose (ED) of quartz samples for dating and retrospective dosimetry. This paper presents simulations of two luminescence dating protocols which use single aliquots of the quartz samples. The first protocol is the well-known single-aliquot regenerative optically stimulated luminescence (SAR-OSL) protocol for quartz. The second protocol was developed more recently and is based on a thermoluminescence (TL) signal measured under isothermal conditions (termed the SAR-ITL technique). The simulations are carried out using a recently published comprehensive kinetic model for quartz, consisting of 11 electron and hole traps and centers. The complete sequence of the two experimental protocols is simulated using the same set of kinetic parameters. The simulated dose response curves for the two protocols are found to be very similar to published experimental data. The relative intrinsic accuracy and precision of the two techniques is estimated by simulating one hundred random variants of the natural samples, and by calculating the equivalent doses using each technique. The 100 simulated natural variants are generated by keeping the transition probabilities between energy levels fixed, while allowing simultaneous random variations of the concentrations of the 11 energy levels. The SAR-OSL protocol was found to be intrinsically both more accurate and more precise than the SAR-ITL protocol. We investigate several experimental factors which affect the precision and accuracy of the two protocols. New simulations are presented for commonly used sensitivity tests consisting of successive cycles of sample irradiation with the same dose, followed by measurements of the sensitivity corrected L/T signals. These new simulations provide valuable insight into the previously reported sensitivity changes taking place during application of the SAR-ITL protocol.