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The generalized hypertree width GHW(H) of a hypergraph H is a measure of its cyclicity. Classes of conjunctive queries or constraint satisfaction problems whose associated hypergraphs have bounded GHW are known to be solvable in polynomial time. However, i ...
This paper introduces a deterministic approximation algorithm with error guarantees for computing the probability of propositional formulas over discrete random variables. The algorithm is based on an incremental compilation of formulas into decision diagr ...
We study highly expressive query languages such as datalog, fixpoint, and while-languages on probabilistic databases. We generalize these languages such that computation steps (e.g. datalog rules) can fire probabilistically. We define two possible semantic ...
Instead of writing SQL queries directly, programmers often prefer writing all their code in a general purpose programming language like Java and having their programs be automatically rewritten to use database queries. Traditional tools such as object-rela ...
Functional Dependency (FD) has been extensively studied in database theory. Most recently there have been some works investigating the implications of extending Description Logics with functional dependencies. In particular the OWL ontology language offers ...
Advances in the technologies of smart mobile devices and tiny sensors together with the increase in the number of web resources open up a plethora of new mobile information services where people can acquire and disseminate information at any place and any ...
Functional Dependency has been extensively studied in database theory. It provides an elegant formalism for specifying key constraints and is the basis for normalization theory used in Relational database design. Given its known axiomatization through logi ...
We study the complexity and expressive power of conjunctive queries over unranked labeled trees represented using a variety of structure relations such as "child'', "descendant'', and "following'' as well as unary relations for node labels. We establish a ...
In conventional programming languages like Java, the interface for accessing databases is often inelegant. Typically, an entire separate database query language must be embedded inside a conventional programming language for programmers to access the full ...
Since the beginning of the multi-core era, database systems research has restarted focusing on increasing concurrency. Even though database systems have been able to accommodate concurrent requests, the exploding number of available cores per chip has surf ...
