58,542 research outputs found
GGDs: Graph Generating Dependencies
We propose Graph Generating Dependencies (GGDs), a new class of dependencies
for property graphs. Extending the expressivity of state of the art constraint
languages, GGDs can express both tuple- and equality-generating dependencies on
property graphs, both of which find broad application in graph data management.
We provide the formal definition of GGDs, analyze the validation problem for
GGDs, and demonstrate the practical utility of GGDs.Comment: 5 page
Consistent Query Answering for Expressive Constraints under Tuple-Deletion Semantics
We study consistent query answering in relational databases. We consider an
expressive class of schema constraints that generalizes both tuple-generating
dependencies and equality-generating dependencies. We establish the complexity
of consistent query answering and repair checking under tuple-deletion
semantics for different fragments of the above constraint language. In
particular, we identify new subclasses of constraints in which the above
problems are tractable or even first-order rewritable
Distribution Constraints: The Chase for Distributed Data
This paper introduces a declarative framework to specify and reason about distributions of data over computing nodes in a distributed setting. More specifically, it proposes distribution constraints which are tuple and equality generating dependencies (tgds and egds) extended with node variables ranging over computing nodes. In particular, they can express co-partitioning constraints and constraints about range-based data distributions by using comparison atoms. The main technical contribution is the study of the implication problem of distribution constraints. While implication is undecidable in general, relevant fragments of so-called data-full constraints are exhibited for which the corresponding implication problems are complete for EXPTIME, PSPACE and NP. These results yield bounds on deciding parallel-correctness for conjunctive queries in the presence of distribution constraints
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