FleXPath: flexible structure and full-text querying for XML
SIGMOD '04 Proceedings of the 2004 ACM SIGMOD international conference on Management of data
Through different eyes: assessing multiple conceptual views for querying web services
Proceedings of the 13th international World Wide Web conference on Alternate track papers & posters
Proceedings of the twenty-fourth ACM SIGMOD-SIGACT-SIGART symposium on Principles of database systems
Efficient query processing in geographic web search engines
Proceedings of the 2006 ACM SIGMOD international conference on Management of data
Relaxing join and selection queries
VLDB '06 Proceedings of the 32nd international conference on Very large data bases
Query relaxation using malleable schemas
Proceedings of the 2007 ACM SIGMOD international conference on Management of data
A semantic approach to contextual advertising
SIGIR '07 Proceedings of the 30th annual international ACM SIGIR conference on Research and development in information retrieval
NaLIX: A generic natural language search environment for XML data
ACM Transactions on Database Systems (TODS)
Relaxation in text search using taxonomies
Proceedings of the VLDB Endowment
Querying Context-Aware Databases
FQAS '09 Proceedings of the 8th International Conference on Flexible Query Answering Systems
Using domain ontologies as semantic dimensions in data warehouses
ER'12 Proceedings of the 31st international conference on Conceptual Modeling
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Traditional information search in which queries are posed against a known and rigid schema over a structured database is shifting towards a Web scenario in which exposed schemas are vague or absent and data comes from heterogeneous sources. In this framework, query answering cannot be precise and needs to be relaxed, with the goal of matching user requests with accessible data. In this paper, we propose a logical model and an abstract query language as a foundation for querying data sets with vague schemas. Our approach takes advantages of the availability of taxonomies, that is, simple classifications of terms arranged in a hierarchical structure. The model is a natural extension of the relational model in which data domains are organized in hierarchies, according to different levels of generalization. The query language is a conservative extension of relational algebra where special operators allow the specification of relaxed queries over vaguely structured information. We study equivalence and rewriting properties of the query language that can be used for query optimization.