The article presents a simple yet optimal approach to compute aggregates of window queries over data streams. The proposal is built as a fully-fledged pipeline of operators that are literal transcripts of mathematical definitions. Main features are an application of the prefix sums and a well-founded un-/slicing technique. The overall process is linear in the number of events and windows, and it takes quasi-constant space for a mix of periodic windows, still applicable to multiple deterministic window queries. The limitations are twofold: the events come in-order and the aggregation function is a left-cancellative monoid.

Streaming systems often use slices to share computation costs among overlapping windows. However they are limited to instantaneous events where only one point represents the event. Here, we extend streams to events that come with a duration, denoted as spanning events. After a short review of the new constraints ensued by event lifespan in a temporal sliding-window context, we propose a new structure for dealing with slices in such an environment, and prove that our technique is both correct and effective to deal with such spanning events.

In this paper, we introduce a hierarchical classification approach in the incremental framework of speaker indexing. The technique of incremental generation of speaker-homogeneous segments is applied in the first phase. Then, we propose a hierarchical classification approach that applied in the speaker indexing framework. This approach benefits from the efficiency of Gaussian mixture model (GMM) merge algorithm to the high accuracy of update Gaussian mixture models which referenced by speakers tree index. The adaptive threshold algorithm reduces the cost of exploring the speakers GMM into the balanced binary tree of speaker's index, whose complexity becomes logarithmic curve

In this paper, we propose a flexible (meta) model for indexing videos, applied to the Moroccan cultural heritage. The model is rather generic, able to describe documentaries, advertisements, movies, and other video types. Our goal is to develop a tool for navigating into a joint database of video and related images, based both on visual contents and manual annotations. We describe mainly the video database schema, the corresponding relational implementation, and our video indexing prototype. The connection with an image sub-database is shortly described. An interesting aspect of our model is its flexibility, which is due, on the one hand, to a parametrised hierarchical decomposition of video types and, on the other hand, to the variety of metadata that can be linked to each decomposition element, though in a controlled way.

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Four major problems that complicate read and write accesses to instances in object-oriented databases are discussed. The four problems are: difficulty in providing ad hoc commutativity relations, lacking overhead, lacking escalation, and pseudo-conflicts. It is shown that all of these problems can be solved by providing a simple form of commutativity. This kind of commutativity is syntactically extracted from the source codes of the methods at compile-time. Then, an efficient linear algorithm calculates the transitive access vectors. Finally, transitive access vectors are translated into classical access modes in order not to incur performance penalty at run-time. Related works on access vectors and field locking are reviewed.>