Consistent Answers Research Articles

Consistency and trust in peer data exchange systems

AbstractWe propose and investigate a semantics for peer data exchange systems where different peers are related by data exchange constraints and trust relationships. These two elements plus the data at the peers' sites and their local integrity constraints are made compatible via a semantics that characterizes sets of solution instances for the peers. They are the intended – possibly virtual – instances for a peer that are obtained through a data repair semantics that we introduce and investigate. The semantically correct answers from a peer to a query, the so-called peer consistent answers, are defined as those answers that are invariant under all its different solution instances. We show that solution instances can be specified as the models of logic programs with a stable model semantics. The repair semantics is based on null values as used in SQL databases, and is also of independent interest for repairs of single databases with respect to integrity constraints.

Mesa

Mesa is a highly scalable analytic data warehousing system that stores critical measurement data related to Google's Internet advertising business. Mesa is designed to satisfy a complex and challenging set of user and systems requirements, including near real-time data ingestion and retrieval, as well as high availability, reliability, fault tolerance, and scalability for large data and query volumes. Specifically, Mesa handles petabytes of data, processes millions of row updates per second, and serves billions of queries that fetch trillions of rows per day. Mesa is geo-replicated across multiple datacenters and provides consistent and repeatable query answers at low latency, even when an entire datacenter fails. This paper presents the Mesa system and reports the performance and scale that it achieves.

Some results on spaces with $\aleph_1$-calibre

We prove that, assuming \emph{CH}, if $X$ is a space with $\aleph_1$-calibre and a zeroset diagonal, then $X$ is submetrizable. This gives a consistent positive answer to the question of Buzyakova in Observations on spaces with zeroset or regular $G_\delta$-diagonals, Comment. Math. Univ. Carolin. 46 (2005), no. 3, 469--473. We also make some observations on spaces with $\aleph_1$-calibre.

Do bipolar subjects' responses to personality questionnaires lack reliability? Evidence from the PsyCoLaus study

Differences in personality scores between subjects with and without mood disorders might result from response biases rather than specific personality traits per se. The aim of this study was to compare subjects with bipolar disorders (BPD) to non-bipolar subjects in terms of response quality to the NEO-FFI. Using data from the population-based cohort study PsyCoLaus, subjects were compared in terms of responses to the NEO-FFI, and indices of response quality were calculated. Hierarchical regression analyses were performed and controlled for sociodemographic factors, depressive episodes, dysthymia, anxiety disorders and substance use disorders. Consistent with the literature, subjects with BPD had higher scores in neuroticism and openness, and lower scores in conscientiousness. However, significant differences were measured for response reliability and validity. In particular, the indices of response quality including response reliability were lower in subjects with BPD suggesting that bipolar subjects might have more difficulty in providing consistent answers throughout questionnaires. However, regression models resulted in small associations between mania/hypomania and response quality, and showed that differences in response quality were mainly attributable to correlates of BPD instead of the presence of mania/hypomania itself. The current findings suggest that bipolar subjects’ responses to questionnaires are biased, making them less reliable.

Estimating the spatial distribution of snow water equivalent in the world's mountains

Estimating the spatial distribution of snow water equivalent (SWE) in mountainous terrain is currently the most important unsolved problem in snow hydrology. Several methods can estimate the amount of snow throughout a mountain range: (1) Spatial interpolation from surface sensors constrained by remotely sensed snow extent provides a consistent answer, with uncertainty related to extrapolation to unrepresented locations. (2) The remotely sensed date of disappearance of snow is combined with a melt calculation to reconstruct the SWE back to the last significant snowfall. (3) Passive microwave sensors offer real‐time global SWE estimates but suffer from several problems like subpixel variability in the mountains. (4) A numerical model combined with assimilated surface observations produces SWE at 1‐km resolution at continental scales, but depends heavily on a surface network. (5) New methods continue to be explored, for example, airborne LiDAR altimetry provides direct measurements of snow depth, which are combined with modelled snow density to estimate SWE. While the problem is aggressively addressed, the right answer remains elusive. Good characterization of the snow is necessary to make informed choices about water resources and adaptation to climate change and variability. WIREs Water 2016, 3:461–474. doi: 10.1002/wat2.1140This article is categorized under: Science of Water > Methods

Exchange-Repairs

In a data exchange setting with target constraints, it is often the case that a given source instance has no solutions. In such cases, the semantics of target queries trivialize. The aim of this paper is to introduce and explore a new framework that gives meaningful semantics in such cases by using the notion of exchange-repairs. Informally, an exchange-repair of a source instance is another source instance that differs minimally from the first, but has a solution. Exchange-repairs give rise to a natural notion of exchange-repair certain answers (XR-certain answers) for target queries. We show that for schema mappings specified by source-to-target GAV dependencies and target equality-generating dependencies (egds), the XR-certain answers of a target conjunctive query can be rewritten as the consistent answers (in the sense of standard database repairs) of a union of conjunctive queries over the source schema with respect to a set of egds over the source schema, making it possible to use a consistent query-answering system to compute XR-certain answers in data exchange. We then examine the general case of schema mappings specified by source-to-target GLAV constraints, a weakly acyclic set of target tgds and a set of target egds. The main result asserts that, for such settings, the XR-certain answers of conjunctive queries can be rewritten as the certain answers of a union of conjunctive queries with respect to the stable models of a disjunctive logic program over a suitable expansion of the source schema.

The Hot Issues and Future Direction of Forensic Document Examination in China

The domain of forensic document examination consists of a variety of professional tasks related to the history and preliminary of questioned documents. The wide area of tasks implemented by forensic document examiners includes the skill to identify the authorship of handwriting and signature; discriminate among genuine, imitated, or disguised handwriting; to examine and analyze components of inks, papers, and other materials connected with documents; and other highly skilled analyses based on specialized technique. The field of handwriting examination is tightly related to empirical knowledge and practical experience. Handwriting is usually thought to be behavioral activities that are identifiable due to the appearance of features and characteristics within the writing. When we assess these features we universally analyze them in two aspects: Both quality and quantity of writing. As mentioned above, the evaluation of quality and quantity is performed by forensic document examiners. The problem is how to conduct this kind of evaluation related to empirical knowledge and experience. There is not consistent answer yet, although many researchers devote themselves to explore in this hot issue, such as mathematical methods applied in handwriting analysis. In this article, several mathematical methods applied to forensic document field are deciphered in domestic perspective of China. In the digital age, we all inevitably deal with problems with the help of computer or computer technology. We also pay close attention to the computer technique assistant in the field of forensic document examination. Standards or criteria of forensic document examination are still hot issues in China. Although we established a few standards or criterion based on requires of practice, it is also a lack of standards or criterion associated to trainees and continuing education in view of practitioners. At the end of this article, the author intends to discuss a piece of a challenge to forensic document examination, which are also universal issues abroad. Those who are critical of the current state of knowledge in this area argue that members of the judiciary have failed to sufficiently address the shortcomings of the forensic document evidence proffered in criminal trials. Specifically, critics of forensic document examination argue that little valuable wording exists in the report to support the validity and reliability of the methodology and findings of forensic document examination.

The Vat. Gr. 191, Manuel Bryennius, and a circle of scholars alternative to that of Maximus Planudes

This article intends to give consistent answers to all the questions that a complex manuscript such as Vat. gr. 191 presents. All the descriptions hitherto published (and an autoptic examination) of this codex give a clear idea of the complexity of its genesis. After highlighting the inconsistencies found in the scientific contributions that aimed at identifying the revisor of this miscellany, this work presents all the information present in Vat. gr. 191 about the revisor, and then matches it with the profile of a prominent scholar of the time, Manuel Bryennius. This hypothesis finds further confirmation in the textual tradition of some of the texts contained in this manuscript, namely, Ptolemy’s Geographia and Diophantus’ Arithmetica.

GeoVanet: A routing protocol for query processing in vehicular networks

In a vehicular ad hoc network VANET, cars can exchange information by using short-range wireless communications. Along with the opportunities offered by vehicular networks, a number of challenges also arise. In particular, most works so far have focused on a push model, where potentially useful data are pushed towards vehicles. The use of pull models, that would allow users to send queries to a set of cars in order to find the desired information, has not been studied in depth. The main challenge for pull models is the difficulty to route the different results towards the query originator in a highly dynamic network where the nodes move very quickly. To solve this issue, we propose GeoVanet, an anonymous and non-intrusive geographic routing protocol which ensures that the sender of a query can get a consistent answer. Our goal is to ensure that the user will be able to retrieve the query results within a bounded time. To prove the effectiveness of GeoVanet, an extensive experimental evaluation has been performed, that proves the interest of the proposal for both rural and urban areas. It shows that up to 80% of the available query results are delivered to the user.

Mary Ellen's conjectures

For a special issue like this, it would seem to be very appropriate for us, the editors, to write an article summarizing Mary Ellen’s contributions to the field, and giving some account of her mathematical career. But there is an excellent article by Frank Tall [65] in the book The Work of Mary Ellen Rudin that does exactly this, covering her work and giving a sketch of her mathematical life up until shortly after her retirement in 1991. The article also includes a list of her students and their theses titles, her postdocs, and her publications. While she published a couple of papers on other topics after that time, she spent most of her post-retirement working on Nikiel’s conjecture, that the images of compact ordered spaces are exactly the compact monotonically normal spaces. She eventually solved it (positively) in 2001 [63]; it took one of the deepest and most difficult arguments of her career to do so. Instead of copying Frank’s article, we would like to do something a bit different. In the book Open Problems in Topology, published in 1990, Mary Ellen has an article [62] in which she states 17 “conjectures”. This is the way she chose to phrase some unsolved problems, most of them due originally to others, that she was particularly interested in. We quote from her article to give a sense of her reasons for choosing these particular problems: “The problems I list here have mostly been listed in Rudin [1988]; I have worked on all of them long enough to have some real respect for them; they have all stood the test of time and labor by various people; and I feel any solution to any of them would have applications at least to other problems exhibiting similar pathologies.” Here we go over Mary Ellen’s list of conjectures, giving a brief summary of her contributions and where each conjecture stands today. Many of these problems had or could be expected to have consistent answers. But Mary Ellen clearly had a bias for ZFC results, so instead of asking “Is it consistent that P holds?” she would ask “Is it true (in ZFC) that “not P” holds?”, or, as in this article, state “Conjecture: Not P holds.”.

Locke, Judgment, and Figure: A Consistent Answer to the Molyneux Problem

John Locke has been famously credited with resurrecting the distinction between common and proper sensibles, better known in the Essay as primary and secondary qualities. Although some argue that Locke’s adherence to the doctrine of the common sensibles is in conflict with his empiricist sensibilities, I will show this is not likely to be the case. In order to achieve this I will argue that Locke held there to be cross-modal connections in the mind for the representational content of ideas of primary quality, through the relation of resemblance, but that these representations need to be empirically verified to be veridical. Consequently, I believe this interpretation points in a useful direction for making an epistemic distinction between objects encountered between the phenomenal and sub-phenomenal domains.

Where do consumers think luxury begins? A study of perceived minimum price for 21 luxury goods in 7 countries

Downward extensions fuel the continuous growth of the luxury sector and the introduction of product lines at accessible prices. Does this blur the traditional concept of luxury associated with expensiveness? Focusing on consumers' perception of the minimum price for a luxury product in 21 categories and seven countries (n=8376), an extreme dispersion across consumers occurs in terms of where luxury begins, with a large majority citing very low price frontiers. Also, each consumer provides consistent answers about the different categories. Such answers indicate that today expensiveness is a relative concept, as is luxury more generally. The degree of immersion in luxury and financial resources influences the luxury price frontier of each consumer. These results suggest a continuum from the “happy few” to the many less privileged. This extreme heterogeneity across consumers is good news for luxury groups. Such heterogeneity offers a large choice for development strategies from traditional luxury to the new luxury.

Perspective: New Service Development: How the Field Developed, Its Current Status and Recommendations for Moving the Field Forward

New service development (NSD) is a growing innovation discipline. Despite the growth of articles about NSD, several authors have criticized the lack of attention paid to NSD, compared with new product development (NPD), and the lack of consensus across NSD findings. At the same time, others have proclaimed that NSD is a sophisticated, mature field of research. This paper tries to resolve these issues by analyzing 230 empirical articles on NSD, published over a period of 30 years. It investigates the content of NSD research articles, the authors contributing to the field, and the research methodologies employed. It finds that, despite its growing popularity, the field has not moved forward substantively. NSD is a subject specialty but lacks an “invisible college” of researchers addressing the topic. This has resulted in a body of research that fails to provide managers with consistent answers to basic questions about how to most effectively manage NSD processes.One of the main causes for the lack of coherence in the knowledge on this topic may stem from the fact that, rather than initially approaching research in the domain without ingoing bias and using grounded theory approaches to create initial understanding, many of the early researchers applied the concepts, frameworks, and methods used to understand NPD to the NSD domain. To correct this problem, it is proposed that the field of NSD needs to move forward in a significantly different manner. This paper provides several recommendations for attracting more academics to the field, elevating the visibility and status of NSD as a research domain, and also presents a research agenda that may help reorient future research in this area so that a more complete and coherent body of knowledge is generated that both advances the field and helps practitioners manage NSD more effectively and efficiently.

What an anticardiovascular diet should be in 2015.

Given scientific and public debate about optimal diet to prevent cardiovascular disease, and interest in diet and other chronic diseases, we propose that following a few simple dietary principles would reduce chronic disease incidence. Nutrition research has been criticized for focusing on individual nutrients and foods, treated like drug therapy. With a few important exceptions, clinical trials of supplemental nutrients have not shown benefit. Although highly specific nutrition information is elusive, diet patterns have provided consistent answers, important for public health. Observational cohort studies have found that some dietary patterns are reported with high reliability over long periods and predict future cardiovascular and other inflammatory-related diseases. Two randomized clinical trials confirmed this finding. There are many common features of Mediterranean and prudent diets, particularly the plant-centered aspect, coupled with variety of foods eaten. A dietary pattern characterized by high fruit, vegetable, legume, whole grain, nut, berry, seed, and fish intakes, and possibly by intakes of dairy, coffee, tea, chocolate, and alcohol (not in excess), but low meat and detrimentally processed foods is associated with reduced incidence of cardiovascular disease and rates of noncardiovascular, noncancer chronic inflammatory-related mortality. A plant-centered diet may be broadly recommended.

Taming primary key violations to query large inconsistent data via ASP

AbstractConsistent query answering over a database that violates primary key constraints is a classical hard problem in database research that has been traditionally dealt with logic programming. However, the applicability of existing logic-based solutions is restricted to data sets of moderate size. This paper presents a novel decomposition and pruning strategy that reduces, in polynomial time, the problem of computing the consistent answer to a conjunctive query over a database subject to primary key constraints to a collection of smaller problems of the same sort that can be solved independently. The new strategy is naturally modeled and implemented using Answer Set Programming (ASP). An experiment run on benchmarks from the database world prove the effectiveness and efficiency of our ASP-based approach also on large data sets.

Words or graphics to present a Discrete Choice Experiment: Does it matter?

ObjectiveTo test whether presenting attribute levels in words or graphics generates different results with respect to attribute level interpretation, relative importance and participation probabilities. MethodsParents of 959 newborns completed a DCE questionnaire that contained two versions of the same nine choice tasks in which the attribute levels were presented in words or graphics. Five attributes related to the decision of parents to vaccinate their newborn against rotavirus were included. Mixed-logit models were conducted to estimate the relative importance of the attribute levels. ResultsRespondents who started with the choice tasks in words produced the most consistent answer patterns. All respondents significantly preferred words to graphics. Part-worth utilities and the relative importance of the attribute levels differed based on the words and graphics data, resulting in different probabilities to participate in vaccination. ConclusionsWords were preferred over graphics, resulted in higher choice consistency, and showed more valid attribute level estimates. Graphics did not improve respondents’ understanding of the attribute levels. Practice implicationsFuture research on the use of either words or graphics is recommended in order to establish guidelines on how to develop a valid presentation method for attribute levels in the choice tasks of a DCE.

Thermal imaging of Bi2212 THz oscillator

Bi2Sr2CaCu2O8+δ (Bi2212) mesas are promising candidates for THz oscillators, which can fill the frequency range around “THz gap”. However, it is known that Bi2212 mesas show self-heating effects (hot spots) when the current is passed along the c-axis due to the low thermal conductivity in this direction. Although several previous studies reported the relation of the hot spot and THz emission, consistent answer has not been obtained yet. In order to address this issue, imaging of temperature distributions on Bi2212 mesas is expected to be very effective. Here, we set up fluorescent thermal imaging (FTI) method for visualizing the surface temperature distribution on the Bi2212 mesa. We have succeeded in observing hot spots in the Bi2212 mesa with high spatial resolution.

Inconsistency-tolerant query answering in ontology-based data access

Ontology-based data access (OBDA) is receiving great attention as a new paradigm for managing information systems through semantic technologies. According to this paradigm, a Description Logic ontology provides an abstract and formal representation of the domain of interest to the information system, and is used as a sophisticated schema for accessing the data and formulating queries over them. In this paper, we address the problem of dealing with inconsistencies in OBDA. Our general goal is both to study DL semantical frameworks that are inconsistency-tolerant, and to devise techniques for answering unions of conjunctive queries under such inconsistency-tolerant semantics. Our work is inspired by the approaches to consistent query answering in databases, which are based on the idea of living with inconsistencies in the database, but trying to obtain only consistent information during query answering, by relying on the notion of database repair. We first adapt the notion of database repair to our context, and show that, according to such a notion, inconsistency-tolerant query answering is intractable, even for very simple DLs. Therefore, we propose a different repair-based semantics, with the goal of reaching a good compromise between the expressive power of the semantics and the computational complexity of inconsistency-tolerant query answering. Indeed, we show that query answering under the new semantics is first-order rewritable in OBDA, even if the ontology is expressed in one of the most expressive members of the DL-Lite family.

Why Is It Hard to Obtain a Dichotomy for Consistent Query Answering?

A database may for various reasons become inconsistent with respect to a given set of integrity constraints. In the late 1990s, the formal approach of consistent query answering was proposed in order to query such databases. Since then, a lot of efforts have been spent to classify the complexity of consistent query answering under various classes of constraints. It is known that for the most common constraints and queries, the problem is in coNP and might be coNP-hard, yet several relevant tractable classes have been identified. Additionally, the results that emerged suggested that given a set of key constraints and a conjunctive query, the problem of consistent query answering is either in PTime or is coNP-complete. However, despite all the work, as of today this dichotomy remains a conjecture. The main contribution of this article is to explain why it appears so difficult to obtain a dichotomy result in the setting of consistent query answering. Namely, we prove that such a dichotomy with respect to common classes of constraints and queries is harder to achieve than a dichotomy for the constraint satisfaction problem, which is a famous open problem since the 1990s.

From Classical to Consistent Query Answering under Existential Rules

Querying inconsistent ontologies is an intriguing new problem that gave rise to a flourishing research activity in the description logic (DL) community. The computational complexity of consistent query answering under the main DLs is rather well understood; however, little is known about existential rules. The goal of the current work is to perform an in-depth analysis of the complexity of consistent query answering under the main decidable classes of existential rules enriched with negative constraints. Our investigation focuses on one of the most prominent inconsistency-tolerant semantics, namely, the AR semantics. We establish a generic complexity result, which demonstrates the tight connection between classical and consistent query answering. This result allows us to obtain in a uniform way a relatively complete picture of the complexity of our problem.