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Section: New Results
Semantic Data Integration
Participants : Michel Chein, Madalina Croitoru, Léa Guizol, Michel Leclère, Rallou Thomopoulos.
It often happens that different references (i.e. data descriptions), possibly coming from heterogeneous data sources, concern the same real world entity. In such cases, it is necessary: (i) to detect whether different data descriptions really refer to the same real world entity and (ii) to fuse them into a unique representation. Since the seminal paper [52] , this issue has been been studied under various names:“record linking”, “entity resolution”,“reference resolution”, ”de-duplication”, “object identification”, “data reconciliation”, etc., mostly in databases (cf. the bibliography by William E. Winckler (http://www.hcp.med.harvard.edu/statistics/survey-soft/docs/WinklerReclinkRef.pdf )). It has become one of the major challenges in the Web of Data, where the objective is to link data published on the web and to process them as a single distributed database. Most entity resolution methods are based on classification techniques; Fatiha Saïs, Nathalie Pernelle and Marie-Christine Rousset proposed the first logical approach [53] . Many experiments on public data are underway, in France (cf. DataLift(DataLift, http://datalift.org/ ) and ISIDORE(ISIDORE, http://www.rechercheisidore.fr/ ) projects) or internationally (e.g., VIAF project(The Virtual International Authority File, http://www.oclc.org/research/activities/viaf/ ) led by OCLC(Online Computer Library Center, http://www.oclc.org ), whose aim is to interconnect authority files coming from 18 national organizations).
Three years ago, we began a collaboration with ABES (National Bibliographic Agency for Universities, which takes part in the VIAF project). The aim of this collaboration is to enable the publication of ABES metadata based on the Web of Data and to provide an identification service dedicated to bibliographic notices. ABES bibliographic bases, and more generally document metadata bases, appear to be a privileged application domain for the representation and reasoning formalisms developed by the team. This work has an interdisciplinary dimension, as it also requires experts in the Library and Information Science domain. We think that a logical approach is able to provide a generic solution for entity resolution in document metedata bases, even though it is generally admitted in Library and Information Science that “there is no single paradigmatic author name disambiguation task—each bibliographic database, each digital library, and each collection of publications, has its own unique set of problems and issues” [54] .
Implementation of an Entity Identification Service
Last year, we have developed a method and a prototype to perform entity resolution between on one hand the authors of a new bibliographic notice, and, on the other the domain experts of an authority catalog (and namely the Sudoc catalogue from the ABES agency). The prototype providing this service has been implemented on top of Cogui and experiments have been led in the context of the SudocAd project (jointly conducted by ABES and GraphIK). This work has been continued this year on the following issues as part of the Qualinca project:
generalizing the developed method with the aim to define a generic combined (numerical/logical) framework for entity resolution. This work is reported in the research report [44] that we plan to submit to a conference in January.
Defining evaluation measures of the quality of an entity resolution tool. This work is still on-going.
Quality of Document Catalogs
The SudocAd project showed the feasability and pertinence of a mixed approach for data interlinking problems. It also showed the immediate necessity of taking into account the existence of human errors already present in document catalogues. This led us to propose Qualinca, an ANR Contint project, accepted beginning 2012 and started in April 2012. The partners include two major actors in the document catalogues field: ABES and INA, as well as three academic research groups.
In this context we currently investigate a formal approach to the notion of a "key" in the web of data. Our immediate objective is to define the notion of a discovered key used then in order to evaluate the quality of data inter linking of a meta data catalogue.
We also study the methodology of linking error detection and fixing based on a partitioning (clustering) method on authors of bibliographic records. This study is part of the PhD thesis of Léa Guizol (jointly funded by GraphIK and ABES). The above mentioned methodology is based on a set of criteria which will allow us to cluster "similar" authors together. Each criterion represents a point of view on the author: name, publication time span, publication domain etc. The first challenge consists of defining for each of such view points the respective criteria. The second challenge is to propose an aggregation semantics of such criteria which is well adapted for the problem at hand.
The methodology of using such clustering techniques for this problem has been published in [25] . A certain number of criteria have already been implemented and different partitioning semantics proposed. We are currently evaluating these on the ABES data.
Multi Agent Knowledge Allocation
The assumption behind semantic data integration and querying is that different agents accessing the integrated data repository will have equal interest in the querying results. This is not always true in a data sensitive scenario where the knowledge provider might want to allocate the query answers to the agents based on their valuations. Furthermore, the agents might want some information exclusively (and thus offer a valuation that allows it) while others might want it shared. To this end we have proposed a new mechanism of allocation of query answers inspired from combinatorial auctions. We have defined the newly introduced scenario of Multi Agent Knowledge Allocation and proposed a graph based method, inspired on network flows, for solving it.