49 research outputs found
InterPoll: Crowd-Sourced Internet Polls
Crowd-sourcing is increasingly being used to provide answers to online polls and surveys. However, existing systems, while taking care of the mechanics of attracting crowd workers, poll building, and payment, provide little to help the survey-maker or pollster in obtaining statistically significant results devoid of even the obvious selection biases.
This paper proposes InterPoll, a platform for programming of crowd-sourced polls. Pollsters express polls as embedded LINQ queries and the runtime correctly reasons about uncertainty in those polls, only polling as many people as required to meet statistical guarantees. To optimize the cost of polls, InterPoll performs query optimization, as well as bias correction and power analysis. The goal of InterPoll is to provide a system that can be reliably used for research into marketing, social and political science questions.
This paper highlights some of the existing challenges and how InterPoll is designed to address most of them.
In this paper we summarize some of the work we have already done and give an outline for future work
An Analytical Study of Large SPARQL Query Logs
International audienceWith the adoption of RDF as the data model for Linked Data and the Semantic Web, query specification from end-users has become more and more common in SPARQL endpoints. In this paper, we conduct an in-depth analytical study of the queries formulated by end-users and harvested from large and up-to-date structured query logs from a wide variety of RDF data sources. As opposed to previous studies, ours is the first assessment on a voluminous query corpus, spanning over several years and covering many representative SPARQL endpoints. Apart from the syntactical structure of the queries, that exhibits already interesting results on this generalized corpus, we drill deeper in the structural characteristics related to the graph and hypergraph representation of queries. We outline the most common shapes of queries when visually displayed as undirected graphs, characterize their tree width, length of their cycles, maximal degree of nodes, and more. For queries that cannot be adequately represented as graphs, we investigate their hypergraphs and hypertree width. Moreover, we analyze the evolution of queries over time, by introducing the novel concept of a streak, i.e., a sequence of queries that appear as subsequent modifications of
Equivalence of Queries with Nested Aggregation
Query equivalence is a fundamental problem within database theory. The correctness of all forms of logical query rewritingâjoin minimization, view flattening, rewriting over materialized views, various semantic optimizations that exploit schema dependencies, federated query processing and other forms of data integrationârequires proving that the final executed query is equivalent to the original user query. Hence, advances in the theory of query equivalence enable advances in query processing and optimization.
In this thesis we address the problem of deciding query equivalence between conjunctive SQL queries containing aggregation operators that may be nested. Our focus is on understanding the interaction between nested aggregation operators and the other parts of the query body, and so we model aggregation functions simply as abstract collection constructors. Hence, the precise language that we study is a conjunctive algebraic language that constructs complex objects from databases of flat relations. Using an encoding of complex objects as flat relations, we reduce the query equivalence problem for this algebraic language to deciding equivalence between relational encodings output by traditional conjunctive queries (not containing aggregation). This encoding-equivalence cleanly unifies and generalizes previous results for deciding equivalence of conjunctive queries evaluated under various processing semantics. As part of our study of aggregation operators that can construct empty sub-collectionsâso-called âscalarâ aggregationâwe consider query equivalence for conjunctive queries extended with a left outer join operator, a very practical class of queries for which the general equivalence problem has never before been analyzed. Although we do not completely solve the equivalence problem for queries with outer joins or with scalar aggregation, we do propose useful sufficient conditions that generalize previously known results for restricted classes of queries. Overall, this thesis offers new insight into the fundamental principles governing the behaviour of nested aggregation
TLAD 2010 Proceedings:8th international workshop on teaching, learning and assesment of databases (TLAD)
This is the eighth in the series of highly successful international workshops on the Teaching, Learning and Assessment of Databases (TLAD 2010), which once again is held as a workshop of BNCOD 2010 - the 27th International Information Systems Conference. TLAD 2010 is held on the 28th June at the beautiful Dudhope Castle at the Abertay University, just before BNCOD, and hopes to be just as successful as its predecessors.The teaching of databases is central to all Computing Science, Software Engineering, Information Systems and Information Technology courses, and this year, the workshop aims to continue the tradition of bringing together both database teachers and researchers, in order to share good learning, teaching and assessment practice and experience, and further the growing community amongst database academics. As well as attracting academics from the UK community, the workshop has also been successful in attracting academics from the wider international community, through serving on the programme committee, and attending and presenting papers.This year, the workshop includes an invited talk given by Richard Cooper (of the University of Glasgow) who will present a discussion and some results from the Database Disciplinary Commons which was held in the UK over the academic year. Due to the healthy number of high quality submissions this year, the workshop will also present seven peer reviewed papers, and six refereed poster papers. Of the seven presented papers, three will be presented as full papers and four as short papers. These papers and posters cover a number of themes, including: approaches to teaching databases, e.g. group centered and problem based learning; use of novel case studies, e.g. forensics and XML data; techniques and approaches for improving teaching and student learning processes; assessment techniques, e.g. peer review; methods for improving students abilities to develop database queries and develop E-R diagrams; and e-learning platforms for supporting teaching and learning
TLAD 2010 Proceedings:8th international workshop on teaching, learning and assesment of databases (TLAD)
This is the eighth in the series of highly successful international workshops on the Teaching, Learning and Assessment of Databases (TLAD 2010), which once again is held as a workshop of BNCOD 2010 - the 27th International Information Systems Conference. TLAD 2010 is held on the 28th June at the beautiful Dudhope Castle at the Abertay University, just before BNCOD, and hopes to be just as successful as its predecessors.The teaching of databases is central to all Computing Science, Software Engineering, Information Systems and Information Technology courses, and this year, the workshop aims to continue the tradition of bringing together both database teachers and researchers, in order to share good learning, teaching and assessment practice and experience, and further the growing community amongst database academics. As well as attracting academics from the UK community, the workshop has also been successful in attracting academics from the wider international community, through serving on the programme committee, and attending and presenting papers.This year, the workshop includes an invited talk given by Richard Cooper (of the University of Glasgow) who will present a discussion and some results from the Database Disciplinary Commons which was held in the UK over the academic year. Due to the healthy number of high quality submissions this year, the workshop will also present seven peer reviewed papers, and six refereed poster papers. Of the seven presented papers, three will be presented as full papers and four as short papers. These papers and posters cover a number of themes, including: approaches to teaching databases, e.g. group centered and problem based learning; use of novel case studies, e.g. forensics and XML data; techniques and approaches for improving teaching and student learning processes; assessment techniques, e.g. peer review; methods for improving students abilities to develop database queries and develop E-R diagrams; and e-learning platforms for supporting teaching and learning
Enabling Complex Semantic Queries to Bioinformatics Databases through Intuitive Search Over Data
Data integration promises to be one of the main catalysts in enabling new insights to be drawn from the wealth of biological data already available publicly. However, the heterogene- ity of the existing data sources still poses significant challenges for achieving interoperability among biological databases. Furthermore, merely solving the technical challenges of data in- tegration, for example through the use of common data representation formats, leaves open the larger problem. Namely, the steep learning curve required for understanding the data models of each public source, as well as the technical language through which the sources can be queried and joined. As a consequence, most of the available biological data remain practically unexplored today.
In this thesis, we address these problems jointly, by first introducing an ontology-based data integration solution in order to mitigate the data source heterogeneity problem. We illustrate through the concrete example of Bgee, a gene expression data source, how relational databases can be exposed as virtual Resource Description Framework (RDF) graphs, through relational-to-RDF mappings. This has the important advantage that the original data source can remain unmodified, while still becoming interoperable with external RDF sources.
We complement our methods with applied case studies designed to guide domain experts in formulating expressive federated queries targeting the integrated data across the domains of evolutionary relationships and gene expression. More precisely, we introduce two com- parative analyses, first within the same domain (using orthology data from multiple, inter- operable, data sources) and second across domains, in order to study the relation between expression change and evolution rate following a duplication event.
Finally, in order to bridge the semantic gap between users and data, we design and im- plement Bio-SODA, a question answering system over domain knowledge graphs, that does not require training data for translating user questions to SPARQL. Bio-SODA uses a novel ranking approach that combines syntactic and semantic similarity, while also incorporating node centrality metrics to rank candidate matches for a given user question. Our results in testing Bio-SODA across several real-world databases that span multiple domains (both within and outside bioinformatics) show that it can answer complex, multi-fact queries, be- yond the current state-of-the-art in the more well-studied open-domain question answering.
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LâintĂ©gration des donnĂ©es promet dâĂȘtre lâun des principaux catalyseurs permettant dâextraire des nouveaux aperçus de la richesse des donnĂ©es biologiques dĂ©jĂ disponibles publiquement. Cependant, lâhĂ©tĂ©rogĂ©nĂ©itĂ© des sources de donnĂ©es existantes pose encore des dĂ©fis importants pour parvenir Ă lâinteropĂ©rabilitĂ© des bases de donnĂ©es biologiques. De plus, en surmontant seulement les dĂ©fis techniques de lâintĂ©gration des donnĂ©es, par exemple grĂące Ă lâutilisation de formats standard de reprĂ©sentation de donnĂ©es, on laisse ouvert un problĂšme encore plus grand. Ă savoir, la courbe dâapprentissage abrupte nĂ©cessaire pour comprendre la modĂ©li- sation des donnĂ©es choisie par chaque source publique, ainsi que le langage technique par lequel les sources peuvent ĂȘtre interrogĂ©s et jointes. Par consĂ©quent, la plupart des donnĂ©es biologiques publiquement disponibles restent pratiquement inexplorĂ©s aujourdâhui.
Dans cette thĂšse, nous abordons lâensemble des deux problĂšmes, en introduisant dâabord une solution dâintĂ©gration de donnĂ©es basĂ©e sur ontologies, afin dâattĂ©nuer le problĂšme dâhĂ©tĂ©- rogĂ©nĂ©itĂ© des sources de donnĂ©es. Nous montrons, Ă travers lâexemple de Bgee, une base de donnĂ©es dâexpression de gĂšnes, une approche permettant les bases de donnĂ©es relationnelles dâĂȘtre publiĂ©s sous forme de graphes RDF (Resource Description Framework) virtuels, via des correspondances relationnel-vers-RDF (« relational-to-RDF mappings »). Cela prĂ©sente lâimportant avantage que la source de donnĂ©es dâorigine peut rester inchangĂ©, tout en de- venant interopĂ©rable avec les sources RDF externes.
Nous complĂ©tons nos mĂ©thodes avec des Ă©tudes de cas appliquĂ©es, conçues pour guider les experts du domaine dans la formulation de requĂȘtes fĂ©dĂ©rĂ©es expressives, ciblant les don- nĂ©es intĂ©grĂ©es dans les domaines des relations Ă©volutionnaires et de lâexpression des gĂšnes. Plus prĂ©cisĂ©ment, nous introduisons deux analyses comparatives, dâabord dans le mĂȘme do- maine (en utilisant des donnĂ©es dâorthologie provenant de plusieurs sources de donnĂ©es in- teropĂ©rables) et ensuite Ă travers des domaines interconnectĂ©s, afin dâĂ©tudier la relation entre le changement dâexpression et le taux dâĂ©volution suite Ă une duplication de gĂšne.
Enfin, afin de mitiger le dĂ©calage sĂ©mantique entre les utilisateurs et les donnĂ©es, nous concevons et implĂ©mentons Bio-SODA, un systĂšme de rĂ©ponse aux questions sur des graphes de connaissances domaine-spĂ©cifique, qui ne nĂ©cessite pas de donnĂ©es de formation pour traduire les questions des utilisateurs vers SPARQL. Bio-SODA utilise une nouvelle ap- proche de classement qui combine la similaritĂ© syntactique et sĂ©mantique, tout en incorporant des mĂ©triques de centralitĂ© des nĆuds, pour classer les possibles candidats en rĂ©ponse Ă une question utilisateur donnĂ©e. Nos rĂ©sultats suite aux tests effectuĂ©s en utilisant Bio-SODA sur plusieurs bases de donnĂ©es Ă travers plusieurs domaines (tantĂŽt liĂ©s Ă la bioinformatique quâextĂ©rieurs) montrent que Bio-SODA rĂ©ussit Ă rĂ©pondre Ă des questions complexes, en- gendrant multiples entitĂ©s, au-delĂ de lâĂ©tat actuel de la technique en matiĂšre de systĂšmes de rĂ©ponses aux questions sur les donnĂ©es structures, en particulier graphes de connaissances