Showing papers by "University of Wisconsin-Madison published in 1999"
TL;DR: This article proposes methods for combining estimates of the cause-specific hazard functions under the proportional hazards formulation, but these methods do not allow the analyst to directly assess the effect of a covariate on the marginal probability function.
Abstract: With explanatory covariates, the standard analysis for competing risks data involves modeling the cause-specific hazard functions via a proportional hazards assumption Unfortunately, the cause-specific hazard function does not have a direct interpretation in terms of survival probabilities for the particular failure type In recent years many clinicians have begun using the cumulative incidence function, the marginal failure probabilities for a particular cause, which is intuitively appealing and more easily explained to the nonstatistician The cumulative incidence is especially relevant in cost-effectiveness analyses in which the survival probabilities are needed to determine treatment utility Previously, authors have considered methods for combining estimates of the cause-specific hazard functions under the proportional hazards formulation However, these methods do not allow the analyst to directly assess the effect of a covariate on the marginal probability function In this article we pro
11,109 citations
21 Mar 1999
TL;DR: This paper investigates the page request distribution seen by Web proxy caches using traces from a variety of sources and considers a simple model where the Web accesses are independent and the reference probability of the documents follows a Zipf-like distribution, suggesting that the various observed properties of hit-ratios and temporal locality are indeed inherent to Web accesse observed by proxies.
Abstract: This paper addresses two unresolved issues about Web caching. The first issue is whether Web requests from a fixed user community are distributed according to Zipf's (1929) law. The second issue relates to a number of studies on the characteristics of Web proxy traces, which have shown that the hit-ratios and temporal locality of the traces exhibit certain asymptotic properties that are uniform across the different sets of the traces. In particular, the question is whether these properties are inherent to Web accesses or whether they are simply an artifact of the traces. An answer to these unresolved issues will facilitate both Web cache resource planning and cache hierarchy design. We show that the answers to the two questions are related. We first investigate the page request distribution seen by Web proxy caches using traces from a variety of sources. We find that the distribution does not follow Zipf's law precisely, but instead follows a Zipf-like distribution with the exponent varying from trace to trace. Furthermore, we find that there is only (i) a weak correlation between the access frequency of a Web page and its size and (ii) a weak correlation between access frequency and its rate of change. We then consider a simple model where the Web accesses are independent and the reference probability of the documents follows a Zipf-like distribution. We find that the model yields asymptotic behaviour that are consistent with the experimental observations, suggesting that the various observed properties of hit-ratios and temporal locality are indeed inherent to Web accesses observed by proxies. Finally, we revisit Web cache replacement algorithms and show that the algorithm that is suggested by this simple model performs best on real trace data. The results indicate that while page requests do indeed reveal short-term correlations and other structures, a simple model for an independent request stream following a Zipf-like distribution is sufficient to capture certain asymptotic properties observed at Web proxies.
3,582 citations
TL;DR: A process model of framing is developed, identifying four key processes that should be addressed in future research: frame building, frame setting, individual-level processes of framing, and a feedback loop from audiences to journalists.
Abstract: Research on framing is characterized by theoretical and empirical vagueness. This is due, in part, to the lack of a commonly shared theoretical model underlying framing research. Conceptual problems translate into operational problems, limiting the comparability of instruments and results. In this paper I systematize the fragmented approaches to framing in political communication and integrate them into a comprehensive model. I classify previous approaches to framing research along two dimensions: the type of frame examined (media frames vs. audience frames) and the way frames are operationalized (independent variable or dependent variable). I develop a process model of framing, identifying four key processes that should be addressed in future research: frame building, frame setting, individual-level processes of framing, and a feedback loop from audiences to journalists.
3,345 citations
TL;DR: In this article, a non-standard asymptotic theory of inference is developed which allows construction of confidence intervals and testing of hypotheses, and the methods are applied to a 15-year sample of 565 US firms to test whether financial constraints affect investment decisions.
3,019 citations
TL;DR: A major unifying thread of the review is a consideration of how the changes occurring during and after ischemia conspire to produce damaging levels of free radicals and peroxynitrite to activate calpain and other Ca(2+)-driven processes that are damaging, and to initiate the apoptotic process.
Abstract: This review is directed at understanding how neuronal death occurs in two distinct insults, global ischemia and focal ischemia. These are the two principal rodent models for human disease. Cell dea...
2,960 citations
10 Jan 1999
TL;DR: The effect of dimensionality on the "nearest neighbor" problem is explored, and it is shown that under a broad set of conditions, as dimensionality increases, the Distance to the nearest data point approaches the distance to the farthest data point.
Abstract: We explore the effect of dimensionality on the "nearest neighbor" problem. We show that under a broad set of conditions (much broader than independent and identically distributed dimensions), as dimensionality increases, the distance to the nearest data point approaches the distance to the farthest data point. To provide a practical perspective, we present empirical results on both real and synthetic data sets that demonstrate that this effect can occur for as few as 10-15 dimensions.
These results should not be interpreted to mean that high-dimensional indexing is never meaningful; we illustrate this point by identifying some high-dimensional workloads for which this effect does not occur. However, our results do emphasize that the methodology used almost universally in the database literature to evaluate high-dimensional indexing techniques is flawed, and should be modified. In particular, most such techniques proposed in the literature are not evaluated versus simple linear scan, and are evaluated over workloads for which nearest neighbor is not meaningful. Often, even the reported experiments, when analyzed carefully, show that linear scan would outperform the techniques being proposed on the workloads studied in high (10-15) dimensionality!
2,012 citations
Posted Content•
TL;DR: This study examines how well the alternative estimators behave econometrically in terms of bias and precision when the data are skewed or have other common data problems (heteroscedasticity, heavy tails, etc).
Abstract: Data on health care expenditures, length of stay, utilization of health services, consumption of unhealthy commodities, etc. are typically characterized by: (a) nonnegative outcomes; (b) nontrivial fractions of zero outcomes in the population (and sample); and (c) positively-skewed distributions of the nonzero realizations. Similar data structures are encountered in labor economics as well. This paper provides simulation-based evidence on the finite-sample behavior of two sets of estimators designed to look at the effect of a set of covariates x on the expected outcome, E(y|x), under a range of data problems encountered in every day practice: generalized linear models (GLM), a subset of which can simply be viewed as differentially weighted nonlinear least-squares estimators, and those derived from least-squares estimators for the ln(y). We consider the first- and second- order behavior of these candidate estimators under alternative assumptions on the data generating processes. Our results indicate that the choice of estimator for models of ln(E(x|y)) can have major implications for empirical results if the estimator is not designed to deal with the specific data generating mechanism. Garden-variety statistical problems - skewness, kurtosis, and heteroscedasticity - can lead to an appreciable bias for some estimators or appreciable losses in precision for others.
1,933 citations
TL;DR: This study reports that flc null mutations result in early flowering, demonstrating that the role of active FLC alleles is to repress flowering, and proposes that the level of FLC activity acts through a rheostat-like mechanism to control flowering time in Arabidopsis and that modulation of F LC expression is a component of the vernalization response.
Abstract: Winter-annual ecotypes of Arabidopsis are relatively late flowering, unless the flowering of these ecotypes is promoted by exposure to cold (vernalization). This vernalization-suppressible, late-flowering phenotype results from the presence of dominant, late-flowering alleles at two loci, FRIGIDA (FRI) and FLOWERING LOCUS C (FLC). In this study, we report that flc null mutations result in early flowering, demonstrating that the role of active FLC alleles is to repress flowering. FLC was isolated by positional cloning and found to encode a novel MADS domain protein. The levels of FLC mRNA are regulated positively by FRI and negatively by LUMINIDEPENDENS. FLC is also negatively regulated by vernalization. Overexpression of FLC from a heterologous promoter is sufficient to delay flowering in the absence of an active FRI allele. We propose that the level of FLC activity acts through a rheostat-like mechanism to control flowering time in Arabidopsis and that modulation of FLC expression is a component of the vernalization response.
1,836 citations
TL;DR: It is proposed that the PFC plays a crucial role in affective working memory and is most directly involved in the representation of elementary positive and negative emotional states while the dorsolateral PFC may be involved inThe representation of the goal states towards which these elementarypositive and negative states are directed.
1,637 citations
TL;DR: Treatment with sustained-release bupropion alone or in combination with a nicotine patch resulted in significantly higher long-term rates of smoking cessation than use of either the nicotine patch alone or placebo.
Abstract: Background and Methods Use of nicotine-replacement therapies and the antidepressant bupropion helps people stop smoking. We conducted a double-blind, placebo-controlled comparison of sustained-release bupropion (244 subjects), a nicotine patch (244 subjects), bupropion and a nicotine patch (245 subjects), and placebo (160 subjects) for smoking cessation. Smokers with clinical depression were excluded. Treatment consisted of nine weeks of bupropion (150 mg a day for the first three days, and then 150 mg twice daily) or placebo, as well as eight weeks of nicotine-patch therapy (21 mg per day during weeks 2 through 7, 14 mg per day during week 8, and 7 mg per day during week 9) or placebo. The target day for quitting smoking was usually day 8. Results The abstinence rates at 12 months were 15.6 percent in the placebo group, as compared with 16.4 percent in the nicotine-patch group, 30.3 percent in the bupropion group (P<0.001), and 35.5 percent in the group given bupropion and the nicotine patch (P<0.001). B...
1,589 citations
TL;DR: The Bayesian framework for analyzing aligned nucleotide sequence data to reconstruct phylogenies, assess uncertainty in the reconstructions, and perform other statistical inferences is developed and a Markov chain Monte Carlo sampler is employed to sample trees and model parameter values from their joint posterior distribution.
Abstract: We further develop the Bayesian framework for analyzing aligned nucleotide sequence data to reconstruct phylogenies, assess uncertainty in the reconstructions, and perform other statistical inferences. We employ a Markov chain Monte Carlo sampler to sample trees and model parameter values from their joint posterior distribution. All statistical inferences are naturally based on this sample. The sample provides a most-probable tree with posterior probabilities for each clade, information that is qualitatively similar to that for the maximum-likelihood tree with bootstrap proportions and permits further inferences on tree topology, branch lengths, and model parameter values. On moderately large trees, the computational advantage of our method over bootstrapping a maximum-likelihood analysis can be considerable. In an example with 31 taxa, the time expended by our software is orders of magnitude less than that a widely used phylogeny package for bootstrapping maximum likelihood estimation would require to achieve comparable statistical accuracy. While there has been substantial debate over the proper interpretation of bootstrap proportions, Bayesian posterior probabilities clearly and directly quantify uncertainty in questions of biological interest, at least from a Bayesian perspective. Because our tree proposal algorithms are independent of the choice of likelihood function, they could also be used in conjunction with likelihood models more complex than those we have currently implemented.
TL;DR: Transcriptional patterns of calorie-restricted animals suggest that caloric restriction retards the aging process by causing a metabolic shift toward increased protein turnover and decreased macromolecular damage.
Abstract: The gene expression profile of the aging process was analyzed in skeletal muscle of mice. Use of high-density oligonucleotide arrays representing 6347 genes revealed that aging resulted in a differential gene expression pattern indicative of a marked stress response and lower expression of metabolic and biosynthetic genes. Most alterations were either completely or partially prevented by caloric restriction, the only intervention known to retard aging in mammals. Transcriptional patterns of calorie-restricted animals suggest that caloric restriction retards the aging process by causing a metabolic shift toward increased protein turnover and decreased macromolecular damage.
TL;DR: The fabrication of synthetic micro- and nano-structured surfaces and the effects of such textured surfaces on cell behavior are reviewed and the hypothesis that the topography of the basement membrane plays an important role in regulating cellular behavior is proposed.
TL;DR: Administration of exogenous leptin appears to induce weight loss in some obese subjects with elevated endogenous serum leptin concentrations and a dose-response relationship with weight and fat loss was observed with subcutaneous recombinant leptin injections in both lean and obese subjects.
Abstract: ContextThe protein hormone leptin is important to the homeostatic regulation
of body weight. Treatment with exogenous leptin may affect weight loss.ObjectiveTo determine the relationship between increasing doses of exogenous
leptin administration and weight loss in both lean and obese adults.DesignA randomized, double-blind, placebo-controlled, multicenter, escalating
dose cohort trial conducted from April 1997 to October 1998.SettingFour university nutrition and obesity clinics and 2 contract clinical
research clinics.ParticipantsFifty-four lean (body mass index, 20.0-27.5 kg/m2; mean [SD]
body weight, 72.0 [9.7] kg) and 73 obese (body mass index, 27.6-36.0 kg/m2; mean [SD] body weight, 89.8 [11.4] kg) predominantly white (80%)
men (n = 67) and women (n = 60) with mean (SD) age of 39 (10.3) years.InterventionsRecombinant methionyl human leptin self-administered by daily morning
subcutaneous injection (0 [placebo], 0.01, 0.03, 0.10, or 0.30 mg/kg). In
part A, lean and obese subjects were treated for 4 weeks; in part B, obese
subjects were treated for an additional 20 weeks. Lean subjects consumed a
eucaloric diet to maintain body weight at the current value, and obese subjects
were prescribed a diet that reduced their daily energy intake by 2100 kJ/d
(500-kcal/d) from the amount needed to maintain a stable weight.Main Outcome MeasuresBody weight, body fat, and incidence of adverse events.ResultsWeight loss from baseline increased with increasing dose of leptin among
all subjects at 4 weeks (P = .02) and among obese
subjects at 24 weeks (P = .01) of treatment. Mean
(SD) weight changes at 4 weeks ranged from −0.4 (2.0) kg for placebo
(n = 36) to −1.9 kg (1.6) kg for the 0.1 mg/kg dose (n = 29). Mean (SD)
weight changes at 24 weeks ranged from −0.7 (5.4) kg for the 0.01 mg/kg
dose (n = 6) to –7.1 (8.5) kg for the 0.30 mg/kg dose (n = 8). Fat mass
declined from baseline as dose increased among all subjects at 4 weeks (P = .002) and among obese subjects at 24 weeks of treatment
(P = .004); more than 95% of weight loss was fat
loss in the 2 highest dose cohorts at 24 weeks. Baseline serum leptin concentrations
were not related to weight loss at week 4 (P = .88)
or at week 24 (P = .76). No clinically significant
adverse effects were observed on major organ systems. Mild-to-moderate reactions
at the injection site were the most commonly reported adverse effects.ConclusionsA dose-response relationship with weight and fat loss was observed with
subcutaneous recombinant leptin injections in both lean and obese subjects.
Based on this study, administration of exogenous leptin appears to induce
weight loss in some obese subjects with elevated endogenous serum leptin concentrations.
Additional research into the potential role for leptin and related hormones
in the treatment of human obesity is warranted.
TL;DR: Analyses of the extirpation of large animals reveal loss of cascades, and the potential of conservation to restore not only predator populations but also the ecosystem-level effects that ramify from their presence is revealed.
Abstract: New studies are documenting trophic cascades in theoretically unlikely systems such as tropical forests and the open ocean. Together with increasing evidence of cascades, there is a deepening understanding of the conditions that promote and inhibit the transmission of predatory effects. These conditions include the relative productivity of ecosystems, presence of refuges and the potential for compensation. However, trophic cascades are also altered by humans. Analyses of the extirpation of large animals reveal loss of cascades, and the potential of conservation to restore not only predator populations but also the ecosystem-level effects that ramify from their presence.
TL;DR: Evidence is provided that males score higher on standard measures of global self-esteem than females, but the difference is small, and potential reasons for the small yet consistent effect size are discussed.
Abstract: Two analyses were conducted to examine gender differences in global self-esteem In analysis I, a computerized literature search yielded 216 effect sizes, representing the testing of 97,121 respondents The overall effect size was 021, a small difference favoring males A significant quadratic effect of age indicated that the largest effect emerged in late adolescence (d = 033) In Analysis II, gender differences were examined using 3 large, nationally representative data sets from the National Center for Education Statistics (NCES) All of the NCES effect sizes, which collectively summarize the responses of approximately 48,000 young Americans, indicated higher male self-esteem (ds ranged from 004 to 024) Taken together, the 2 analyses provide evidence that males score higher on standard measures of global self-esteem than females, but the difference is small Potential reasons for the small yet consistent effect size are discussed
TL;DR: A new reverse-genetics system that allows one to efficiently generate influenza A viruses entirely from cloned cDNAs is described, which should be useful in viral mutagenesis studies and in the production of vaccines and gene therapy vectors.
Abstract: We describe a new reverse-genetics system that allows one to efficiently generate influenza A viruses entirely from cloned cDNAs. Human embryonic kidney cells (293T) were transfected with eight plasmids, each encoding a viral RNA of the A/WSN/33 (H1N1) or A/PR/8/34 (H1N1) virus, flanked by the human RNA polymerase I promoter and the mouse RNA polymerase I terminator—together with plasmids encoding viral nucleoprotein and the PB2, PB1, and PA viral polymerases. This strategy yielded >1 × 103 plaque-forming units (pfu) of virus per ml of supernatant at 48 hr posttransfection. The addition of plasmids expressing all of the remaining viral structural proteins led to a substantial increase in virus production, 3 × 104–5 × 107 pfu/ml. We also used reverse genetics to generate a reassortant virus containing the PB1 gene of the A/PR/8/34 virus, with all other genes representing A/WSN/33. Additional viruses produced by this method had mutations in the PA gene or possessed a foreign epitope in the head of the neuraminidase protein. This efficient system, which does not require helper virus infection, should be useful in viral mutagenesis studies and in the production of vaccines and gene therapy vectors.
TL;DR: Four cycles of cisplatin plus etoposide and a course of radiotherapy beginning with cycle 1 of the chemotherapy resulted in overall two- and five-year survival rates of 44 percent and 23 percent, a considerable improvement in survival rates over previous results.
Abstract: Background For small-cell lung cancer confined to one hemithorax (limited small-cell lung cancer), thoracic radiotherapy improves survival, but the best ways of integrating chemotherapy and thoracic radiotherapy remain unsettled. Twice-daily accelerated thoracic radiotherapy has potential advantages over once-daily radiotherapy. Methods We studied 417 patients with limited small-cell lung cancer. All the patients received four 21-day cycles of cisplatin plus etoposide. We randomly assigned these patients to receive a total of 45 Gy of concurrent thoracic radiotherapy, given either twice daily over a three-week period or once daily over a period of five weeks. Results Twice-daily treatment beginning with the first cycle of chemotherapy significantly improved survival as compared with concurrent once-daily radiotherapy (P=0.04 by the log-rank test). After a median follow-up of almost 8 years, the median survival was 19 months for the once-daily group and 23 months for the twice-daily group. The survival rat...
TL;DR: Reviews of the literature concerning deserts, boreal forests, tropical forests, lakes, and wetlands lead to the conclusion that extant data are insufficient to conclusively resolve the relationship between diversity and productivity, or that patterns are variable with mechanisms equally varied and complex.
Abstract: ▪ Abstract Recent overviews have suggested that the relationship between species richness and productivity (rate of conversion of resources to biomass per unit area per unit time) is unimodal (hump-shaped). Most agree that productivity affects species richness at large scales, but unanimity is less regarding underlying mechanisms. Recent studies have examined the possibility that variation in species richness within communities may influence productivity, leading to an exploration of the relative effect of alterations in species number per se as contrasted to the addition of productive species. Reviews of the literature concerning deserts, boreal forests, tropical forests, lakes, and wetlands lead to the conclusion that extant data are insufficient to conclusively resolve the relationship between diversity and productivity, or that patterns are variable with mechanisms equally varied and complex. A more comprehensive survey of the ecological literature uncovered approximately 200 relationships, of which 3...
TL;DR: In this article, the authors examined the effects of the type of mentoring relationship and the gender composition of the relationship on mentoring functions and career outcomes reported by 352 female and 257 male proteges.
Abstract: The authors examined the effects of the type of mentoring relationship and the gender composition of the relationship on mentoring functions and career outcomes reported by 352 female and 257 male proteges. Proteges of informal mentors viewed their mentors as more effective and received greater compensation than proteges of formal mentors. Proteges with informal mentors also received more career outcomes than nonmentored individuals, but no significant differences were found between nonmentored and formally mentored individuals. The gender composition of the relationship affected mentoring functions and outcomes, and protege gender interacted with the type of relationship to affect mentoring functions.
TL;DR: The leading edge of lamellipodia in Xenopus laevis keratocytes and fibroblasts was shown to have an extensively branched organization of actin filaments, which is supported by a dendritic brush, suggesting that ADF/cofilin, per se, is not sufficient for actin brush depolymerization and a regulatory step is required.
Abstract: The leading edge (approximately 1 microgram) of lamellipodia in Xenopus laevis keratocytes and fibroblasts was shown to have an extensively branched organization of actin filaments, which we term the dendritic brush. Pointed ends of individual filaments were located at Y-junctions, where the Arp2/3 complex was also localized, suggesting a role of the Arp2/3 complex in branch formation. Differential depolymerization experiments suggested that the Arp2/3 complex also provided protection of pointed ends from depolymerization. Actin depolymerizing factor (ADF)/cofilin was excluded from the distal 0.4 micrometer++ of the lamellipodial network of keratocytes and in fibroblasts it was located within the depolymerization-resistant zone. These results suggest that ADF/cofilin, per se, is not sufficient for actin brush depolymerization and a regulatory step is required. Our evidence supports a dendritic nucleation model (Mullins, R.D., J.A. Heuser, and T.D. Pollard. 1998. Proc. Natl. Acad. Sci. USA. 95:6181-6186) for lamellipodial protrusion, which involves treadmilling of a branched actin array instead of treadmilling of individual filaments. In this model, Arp2/3 complex and ADF/cofilin have antagonistic activities. Arp2/3 complex is responsible for integration of nascent actin filaments into the actin network at the cell front and stabilizing pointed ends from depolymerization, while ADF/cofilin promotes filament disassembly at the rear of the brush, presumably by pointed end depolymerization after dissociation of the Arp2/3 complex.
TL;DR: In this paper, a review of direct and indirect methods used to estimate leaf area index (L), fraction of absorbed photosynthetically active radiation (fAPAR), and net primary production (NPP) from remotely sensed products is presented.
TL;DR: Protocols have been developed for nonmydriatic fundus photography and for evaluation of retinal vascular abnormalities in the ARIC Study and several microvascular changes were significantly associated with higher blood pressure, controlling for gender, race, age, and smoking status.
TL;DR: It is demonstrated that ATM and the hMre11/hRad50/Nbs1 protein complex act in the same DNA damage response pathway and link hMRE11 to the complex pathology of A-T.
TL;DR: Transplantation in a rat model of a human myelin disease shows that ES cell-derived precursors interact with host neurons and efficiently myelinate axons in brain and spinal cord.
Abstract: Self-renewing, totipotent embryonic stem (ES) cells may provide a virtually unlimited donor source for transplantation. A protocol that permits the in vitro generation of precursors for oligodendrocytes and astrocytes from ES cells was devised. Transplantation in a rat model of a human myelin disease shows that these ES cell-derived precursors interact with host neurons and efficiently myelinate axons in brain and spinal cord. Thus, ES cells can serve as a valuable source of cell type-specific somatic precursors for neural transplantation.
TL;DR: A novel scene reconstruction technique is presented, different from previous approaches in its ability to cope with large changes in visibility and its modeling of intrinsic scene color and texture information.
Abstract: A novel scene reconstruction technique is presented, different from previous approaches in its ability to cope with large changes in visibility and its modeling of intrinsic scene color and texture information. The method avoids image correspondence problems by working in a discretized scene space whose voxels are traversed in a fixed visibility ordering. This strategy takes full account of occlusions and allows the input cameras to be far apart and widely distributed about the environment. The algorithm identifies a special set of invariant voxels which together form a spatial and photometric reconstruction of the scene, fully consistent with the input images. The approach is evaluated with images from both inward-facing and outward-facing cameras.
TL;DR: It is demonstrated that high levels of plasmid DNA expression in hepatocytes can be easily obtained by tail vein injections and has great potential for a wide variety of laboratory studies.
Abstract: We have previously shown that the intramuscular injection of naked plasmid DNA enables foreign gene expression in muscle. Further studies showed that the intravascular delivery of naked plasmid DNA enables high levels of expression not only in muscle but also in hepatocytes. For the liver, this technique required injection directly into the liver vessels (portal vein, hepatic vein, or bile duct) and occlusion of outflow. The present study now demonstrates that high levels of plasmid DNA expression in hepatocytes can be easily obtained by tail vein injections. The highest levels of expression are achieved by rapidly injecting the plasmid DNA in large volumes, ~2.5 ml. This technique has great potential for a wide variety of laboratory studies.
TL;DR: In this paper, high-resolution transmission electron microscopy (HRTEM) and X-ray diffraction (XRD) peak broadening (Scherer) analysis were used to study coarsening and morphology development of nanocrystals.
01 Jan 1999
TL;DR: A family of abstract-interpretation algorithms that are capable of determining "shape invariants" of programs that perform destructive updating on dynamically allocated storage by varying the vocabulary used in the three-valued logic.
Abstract: We present a family of abstract-interpretation algorithms that are capable of determining "shape invariants" of programs that perform destructive updating on dynamically allocated storage. The main idea is to represent the stores that can possibly arise during execution using three-valued logical structures.Questions about properties of stores can be answered by evaluating predicate-logic formulae using Kleene's semantics of three-valued logic: If a formula evaluates to true, then the formula holds in every store represented by the three-valued structure.If a formula evaluates to false, then the formula does not hold in any store represented by the three-valued structure.If a formula evaluates to unknown, then we do not know if this formula always holds, never holds, or sometimes holds and sometimes does not hold in the stores represented by the three-valued structure.Three-valued logical structures are thus a conservative representation of memory stores.The approach described is a parametric framework: It provides the basis for generating a family of shape-analysis algorithms by varying the vocabulary used in the three-valued logic.