Incomplete Information in Relational Databases
Journal of the ACM (JACM)
On the representation and querying of sets of possible worlds
Selected papers of the workshop on Deductive database theory
The complexity of querying indefinite data about linearly ordered domains
Journal of Computer and System Sciences - Special issue: dedicated to the memory of Paris Kanellakis
ACM Transactions on Database Systems (TODS)
Complexity of answering queries using materialized views
PODS '98 Proceedings of the seventeenth ACM SIGACT-SIGMOD-SIGART symposium on Principles of database systems
Data on the Web: from relations to semistructured data and XML
Data on the Web: from relations to semistructured data and XML
Efficient string matching: an aid to bibliographic search
Communications of the ACM
Problem of Incomplete Information in Relational Databases
Problem of Incomplete Information in Relational Databases
Data integration: a theoretical perspective
Proceedings of the twenty-first ACM SIGMOD-SIGACT-SIGART symposium on Principles of database systems
On the decidability and complexity of query answering over inconsistent and incomplete databases
Proceedings of the twenty-second ACM SIGMOD-SIGACT-SIGART symposium on Principles of database systems
Conjunctive queries over trees
Journal of the ACM (JACM)
Representing and querying XML with incomplete information
ACM Transactions on Database Systems (TODS)
XML data exchange: Consistency and query answering
Journal of the ACM (JACM)
Modeling and querying probabilistic XML data
ACM SIGMOD Record
Fast and Simple Relational Processing of Uncertain Data
ICDE '08 Proceedings of the 2008 IEEE 24th International Conference on Data Engineering
Certain answers for XML queries
Proceedings of the twenty-ninth ACM SIGMOD-SIGACT-SIGART symposium on Principles of database systems
XML with incomplete information
Journal of the ACM (JACM)
Relational and XML Data Exchange
Relational and XML Data Exchange
Conjunctive query containment over trees
Journal of Computer and System Sciences
Journal of Computer and System Sciences
Incomplete information and certain answers in general data models
Proceedings of the thirtieth ACM SIGMOD-SIGACT-SIGART symposium on Principles of database systems
Probabilistic Databases
An update on query answering with restricted forms of negation
RR'12 Proceedings of the 6th international conference on Web Reasoning and Rule Systems
Containment of pattern-based queries over data trees
Proceedings of the 16th International Conference on Database Theory
When is naive evaluation possible?
Proceedings of the 32nd symposium on Principles of database systems
Reasoning about pattern-based XML queries
RR'13 Proceedings of the 7th international conference on Web Reasoning and Rule Systems
Hi-index | 0.00 |
Previous studies of incomplete XML documents have identified three main sources of incompleteness -- in structural information, data values, and labeling -- and addressed data complexity of answering analogs of unions of conjunctive queries under the open world assumption. It is known that structural incompleteness leads to intractability, while incompleteness in data values and labeling still permits efficient computation of certain answers. The goal of this paper is to provide a complete picture of the complexity of query answering over incomplete XML documents. We look at more expressive languages, at other semantic assumptions, and at both data and combined complexity of query answering, to see whether some well-behaving tractable classes have been missed. To incorporate non-positive features into query languages, we look at gentle ways of introducing negation via inequalities and/or Boolean combinations of positive queries, as well as the analog of relational calculus. We also look at the closed world assumption which, due to the hierarchical structure of XML, has two variations. For all combinations of languages and semantics of incompleteness we determine data and combined complexity of computing certain answers. We show that structural incompleteness leads to intractability under all assumptions, while by dropping it we can recover efficient evaluation algorithms for some queries that go beyond those previously studied.