PC stands for path-conjunctive, the name of a class of queries and dependencies that we define over complex values with dictionaries. This class includes the relational conjunctive queries and embedded dependencies, as well as many interesting examples of complex value and oodb queries and integrity constraints. We show that some important classical results on containment, dependency implicatio...

The chase procedure, an algorithm proposed 25+ years ago to fix constraint violations in database instances, has been successfully applied in a variety of contexts, such as query optimization, data exchange, and data integration. Its practicability, however, is limited by the fact that – for an arbitrary set of constraints – it might not terminate; even worse, chase termination is an undecidabl...

We present a generalization of a strategy, called SCIKD, proposed in [7] that allows to reduce a disclosure risk of confidential data in an information system S [10] using methods based on knowledge discovery. The method proposed in [7] protects confidential data against Rule-based Chase, the null value imputation algorithm driven by certain rules [2], [4]. This method identifies a minimal subs...

We describe here a new concept of one group chasing another, called ‘group chase and escape’, by presenting a simple model. We will show that even a simple model can demonstrate rather rich and complex behavior. In particular, there are cases where an optimal number of chasers exists for a given number of escapees (or targets) to minimize the cost of catching all targets. We have also found an ...

In this work, we present a semantic query optimization technique to improve the efficiency of the evaluation of a subset of SQL:1999 recursive queries. Using datalog notation, we can state our main contribution as an algorithm that builds a program P ′ equivalent to a given program P , when both are applied over a database d satisfying a set of functional dependencies. The input program P is a ...

Rare diseases provide the physician with an exciting opportunity to escape from what may be perceived as boring routine. This endeavour, however, may hold dangers, particularly if the physician has never before encountered the disease in real life. All too easily, an open-mind approach is abandoned. From then on, new data will be used in a relentless quest to support a pre-formed diagnosis [1]....

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