The VLDB Journal (2008) 17:1407–1444
SPECIAL ISSUE PAPER
System support for exploration and expert feedback in resolving
conﬂicts during integration of metadata
K. Selçuk Candan · Huiping Cao · Yan Qi ·
Maria Luisa Sapino
Received: 15 September 2007 / Revised: 6 June 2008 / Accepted: 20 June 2008 / Published online: 7 August 2008
© Springer-Verlag 2008
Abstract A critical reality in integration is that knowledge
obtained from different sources may often be conﬂicting.
Conﬂict-resolution, whether performed during the design
phase or during run-time, can be costly and, if done without a
proper understanding of the usage context, can be ineffective.
In this paper, we propose a novel exploration and feedback-
based approach [FICSR (Pronounced as “ﬁxer”)] to conﬂict-
resolution when integrating metadata from different sources.
Rather than relying on purely automated conﬂict-resolution
mechanisms, FICSR brings the domain expert in the conﬂict-
resolution process and informs the integration based on the
expert’s feedback. In particular, instead of relying on tradi-
tional model based definition of consistency (which, when-
ever there are conﬂicts, picks a possible world among many),
we introduce a ranked interpretation of the metadata and
statements about the metadata. This not only enables FICSR
to avoid committing to an interpretation too early, but also
helps in achieving a more direct correspondence between
the experts’ (subjective) interpretation of the data and the
This research has been funded with NSF Grant, AOC: Archaeological
Data Integration for the Study of Long-Term Human and Social
This work was done while the M. L. Sapino was at ASU for sabbatical.
K. S. Candan (
) · H. Cao · Y. Q i
Computer Science and Engineering,
Arizona State University, Tempe, AZ, USA
Y. Q i
M. L. Sapino
Dip. di Informatica, Univ. di Torino, Torino, Italy
system’s (objective) treatment of the available alternatives.
Consequently, the ranked interpretation leads to new oppor-
tunities for exploratory feedback for conﬂict-resolution:
within the context of a given statement of interest, (a) a pre-
liminary rankingof candidate matches, representing different
resolutions of the conﬂicts, informs the user about the alterna-
tive interpretations of the metadata, while (b) user feedback
regarding the preferences among alternatives is exploited to
inform the system about the expert’s relevant domain knowl-
edge. The expert’s feedback, then, is used for resolving not
only the conﬂicts among different sources, but also possible
mis-alignments due to the initial matching phase. To enable
←→ user) feedback process, we develop data
structures and algorithms for efﬁcient off-line conﬂict/agree-
ment analysis of the integrated metadata. We also develop
algorithms for efﬁcient on-line query processing, candidate
result enumeration, validity analysis, and system feedback.
The results are brought together and evaluated in the Feed-
back-based InConSistency Resolution (FICSR)system.
Keywords Metadata integration · Feedback-based
conﬂict-resolution · Taxonomy · User feedback ·
System feedback · Exploration of alternatives
In this paper, we focus on the problem of integrating meta-
data, such as ontologies, taxonomies, and value hierarchies
commonly used to support context aware data management.
Integration of metadata from different sources starts with
a matching/alignment phase. Different matching techniques
focus on different dimensions of the problem, including
whether data instances are used for schema matching,