The inaugural lecture will take place at amphitheatre Halbwachs at Collège de France, Thursday March 8th 2012 at 18h.
The lectures will start next Wednesday from 10 to 11 AM followed by a seminar given by illustrious guests. You can find the calendar with more details about the guests and the date either :
The “Web Data Management and Distribution” book by Serge Abiteboul, Ioana Manolescu, Philippe Rigaux, Marie-Christine & Pierre Senellart (nicknamed Jorge) is officially launched on the Web: http://webdam.inria.fr/Jorge/
It comes in full in PDF with slides and programming projects.
The book is available at Cambridge University Press
The Webdam Workshop on Brainstorming on Foundations of Web Data Management took place on August 28th, 2009 at Télécom ParisTech. It was an occasion to present Webdam first achievements to a panel of specially talented researchers, all known as being a leading force in their respective research fields. It was also an occasion to share and compare different and useful visions of how the data management of the web should be founded theoritically.
In particular, we got the following exciting presentations :
- Serge Abiteboul, Webdam in brief: Serge presented the main motivations and goals of Webdam: noticing that management of distributed data on the web is not supported by robust models and theory, he proposes to focus on information residing in autonomous systems, following the direction of Axml. This talk raised interesting debate with the audience on concurrency control and more generally on expectations about Webdam.
- Marie-Christine Rousset, Representing and Reasoning on Web Data Semantics, Survey and Challenges: Marie-Christine presented the importance of data semantics to constrain meta-data for web data management. This will allow reasoning on knowledge using logic. This talk raised questions on the best kind of logic to use, the limitations of RDF and extensions to numeric properties.
- Stefano Ceri, Search Computing: Stefano presented his work on the ERC project Search Computing, mostly focused on data management and query optimization. This talk build natural bridges with Webdam, since the use of a rich data will deeply improve quality of search and process modeling; social network are also a natural path for promising interaction. This research also raises questions about the link between search and probabilistic databases.
- Georg Gottlob, Web Data Extraction — Present and Future: Georg’s talk argued on the need of tools to bridge the gap between unstructured and structured information to feed the data management system. He proposed a langage for expressing such extraction methods and tools to support it. It raised questions about creating new annotations on Datalog and managing duplicates.
- Tova Milo, Querying Past and Future in Web Applications: Tova presented applications which would more naturally grow on top of a rich distributed data management system. In particular, she focused on the need to understand and optimize the interaction with the user, considering past interactions. The main challenges which animated the debate is the generalization of the application to a more generic scenario, using in particular a representation of workflows.
- Peter Buneman, Provenance in databases and workflow: Peter’s talk demonstrated the importance of where-, how- and why-provenance. It provided some tools and model to use in presence of complex workflows. This topic is of direct interest for Webdam, since keeping trace of provenance is fundamental in such distributed environments.
- Dan Suciu, Belief Databases: Dan demonstrated the importance of the management of belief in distributed data management system where each user has a consistent view of the database even if inconsistencies may appears across views. This talk raised interesting discussion on the representation of belief and the kind of logic to use in such a system.
- Val Tannen, Provenance Propagation: Val developed the analysis of the previous speakers about the need of provenance to update and feedback propagation in a web data management system. He proposed an algebraic view of provenance in order to better understand it and get general results. The debate focused on summarization of why-provenance and levels of abstraction.
- Victor Vianu, Static Analysis of Active XML Systems: Axml is a first model of web data management system which may support tasks, controlled by guards. Victor presented how properties of the system could be expressed in tree-LTL logic and verified, providing theoretical insurance on the behavior of the system.
- Pierre Senellart, Probabilistic XML: Survey and Challenges: Pierre presented how XML probabilistic databases could leverage the uncertainty to better represent the knowledge on a distributed data management system. He also explained how to reason on this database. It raised exiting challenges like continuous probabilistic distributions and dependency tractability.
- Luc Segoufin, Links with FoX Project: Fox is an european project which focuses on safe processing of dynamic data over Internet. It deals with similar problems as Webdam: data modeling and specification, querying, extracting and exchanging XML data, modeling and verification of temporal behavior and handling incomplete informations. The two projects have already produced fruitful collaboration.
- Balder ten Cate, Structural Characterizations of Schema Mapping Languages: Balder presented how important schema mappings are for data integration on a distributed data management system. He proposed a study of the languages of data mapping schema. It raised interesting issues on adapting this model to XML data and schema mapping optimization.
- Serge Abiteboul, Recent works around AXML: In this presentation, Serge introduced an existing application of Axml: the business artifact. This allows representing a workflow in a data-centric way, well suited for highly distributed applications. This raised a large number of questions about interaction between autonomous system, synchronization, movement of artifacts, monitoring, quality of services, access control…
Werner Nutt is visiting Webdam from Monday 20 April to Friday 24 April 2009. He is a professor at the Faculty of Computer Science at the Free University of Bozen-Bolzano.
He will present his work on containment of conjunctive queries over databases with null values Friday at 2:00pm in the meeting room G008.
Title : Containment of Conjunctive Queries over Databases with Null Values (Joint work with Carles Farre, Ernest Teniente, and Toni Urpi, UPC Barcelona)
Summary : Intuitively, one query “contains” another query if it is more general than the other query. Query containment is a key topic in database theory, which was originally motivated as a foundation of query optimisation, but has also other applications, such as integrity checking and information integration.
The containment problem has been studied for many different types of queries. The work so far, however, has never considered the effect of SQL style null values, although they are ubiquitous in real world data and queries have to process them.
In this talk we discuss in which ways null-containment, that is, containment in the presence of null values, differs from the non-null case. We consider conjunctive queries, which are essentially single block SQL queries. We show that null-containment, as in the non-null case, is NP-complete for boolean queries, which return only yes or no, while the situation becomes different from the classical case for queries that output data. We also discuss sufficient, but non-necessary criteria for null-containment, special cases with polynomial complexity, the effect of “is null” tests, as well as null-containment for richer classes of queries where comparisons or unions are allowed.
Short Bio : Werner Nutt is a professor at the Faculty of Computer Science at the Free University of Bozen-Bolzano in the Italian Alps (since 2005). He obtained a PhD and a habilitation from the university of Saarbruecken, was a visiting associate professor in Jerusalem (1997-2000) and a reader at Heriot-Watt University in Edinburgh (2000-2005). His research interests are in Artificial Intelligence and Databases, with a focus on Description Logics, Information Integration and Incomplete Information.
Bruno Marnette is visiting Webdam Thursday 16 April 2009. He is a phD student at the computing laboratory of the Oxford University.
He will present his work on schema mappings Thursday at 10:30am at ENS Cachan in LSV-library.
Title : Schema-Mappings: From Termination To Tractability
Summary : Data-Exchange is the problem of creating automatically a new database while integrating the information encoded in (1) a given source database and (2) a high-level specification called schema-mapping. After investing the general properties of (generalised) schema-mappings and their semantics, I will introduce in this talk a new sufficient condition TOC for polynomial data-complexity. This criteria TOC generalizes strictly and substantially the best previously-known criteria called Weak-Acyclicity and relies on the termination of (a refinement of) a known procedure called Oblivious Chase. While TOC is RE-complete, I will finally present a more restrictive criteria SwA (for Super-weak Acylicity) that can be decided in polynomial time while generalizing already substantially the notion of Weak Acyclicity.
Diego Calvanese is visiting Webdam from Monday 23 February to Friday 27 February 2009. He is a professor at the Faculty of Computer Science at the Free University of Bozen-Bolzano.
He will present his work on Ontology-Based Data Access and Data Integration Wednesday at 2:00pm in the meeting room N107.
Title : Ontology-Based Data Access and Data Integration
Summary :Ontologies provide a conceptualization of a domain of interest. Nowadays, they are typically represented in terms of Description Logics, and are seen as the key technology used to describe the semantics of information at various sites. The idea of using ontologies as a conceptual view over data repositories is becoming more and more popular. In order for this idea to become widespread in standard applications, it is fundamental that the conceptual layer through which the underlying data layer is accessed does not introduce a significant overhead in dealing with the data. Based on these observations, in recent years techniques to access data sources through a conceptual layer built on top of them have been developed, and the computational complexity of answering queries over ontologies, measured in the size of the underlying data, has been studied. In the talk we will present the general ideas underlying ontology based data access and integration, and will discuss the tradeoff between expressive power of the ontology language, and efficiency in query processing. Specifically, we will address the possibility of delegating query processing in ontology based data access to a relational database engine and will also present the QuOnto system, implementing this approach.