Adaptive query processors make decisions as to the most effective evaluation strategy for a query based on feedback received while the query is being evaluated. In essence, any of the decisions made by the optimizer (e.g., on operator order or on which operators to use) may be revisited in an adaptive query processor. This paper focuses on changes to physical operators (e.g., the specific join ...

The use of business intelligence tools and other means to generate queries has led to great variety in the size of join queries. While most queries are reasonably small, join queries with up to a hundred relations are not that exotic anymore, and the distribution of query sizes has an incredible long tail. The largest real-world query that we are aware of accesses more than 4,000 relations. Thi...

At the heart of aspect-oriented programming is the exposure of certain phenomena in the execution of one set of program elements to behavioral modifications specified by other elements. The phenomena are join points. The modifying elements are aspects. The problem that we address is that current aspectoriented languages do not provide adequate means to control the exposure of join points for be...

In recent years, we have witnessed a massive acquisition of data and increasing need to support multi-criteria decision support (MCDS) queries efficiently. Pareto-optimal also known as skyline queries is a popular class of MCDS queries and has received a lot of attention resulting in a flurry of efficient skyline algorithms. The vast majority of such algorithms focus entirely on the input being...

XML queries can be modeled by twig pattern queries (TPQs) specifying predicates on XML nodes and XPath relationships satisfied between them. A lot of TPQ types have been proposed; this paper takes into account a TPQ model extended by a specification of output and non-output query nodes since it complies with the XQuery semantics and, in many cases, it leads to a more efficient query processing....

The title compound, C7H7N3, is an ortho-rhom-bic polymorph that crystallizes in the space group Pca21. The previously reported monoclinic form [Geiger & Parsons (2013 ▶) Acta Cryst. E69, o452] crystallizes in the space group P21/c (Z = 4). In the crystal, two independent HN-H⋯N C hydrogen bonds link the mol-ecules into chains along the a-glide plane. Two further independent HN-H⋯NH2 hydrogen bo...

We consider exponentiable objects in lax slices of Top with respect to the specialization order (and its opposite) on a base space B. We begin by showing that the lax slice over B has binary products which are preserved by the forgetful functor to Top if and only if B is a meet (respective, join) semilattice in Top, and go on to characterize exponentiability over a complete Alexandrov space B.

Inequality joins, which join relational tables on inequality conditions, are used in various applications. While there have been a wide range of optimization methods for joins in database systems, from algorithms such as sort-merge join and band join, to various indices such as B-tree, R⇤-tree and Bitmap, inequality joins have received little attention and queries containing such joins are usua...

Joining massive tables in relational databases have received substantial attention in the past decade. Numerous filtration and indexing techniques have been proposed to reduce the curse of dimensionality. This paper proposes a novel approach to map the problem of pairwise whole genome comparison into an approximate join operation in the wellestablished relational database context. We propose a ...

This paper addresses the problem of physical query processing for large object-oriented, temporal knowledge bases. The major tasks being investigated are how to generate the space of all possible execution plans for a given knowledge base query and how to traverse this space in order to choose an eecient execution plan. The results of this work include: (a) the formulation of a set of access le...